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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">OL</journal-id>
<journal-title-group>
<journal-title>Oncology Letters</journal-title>
</journal-title-group>
<issn pub-type="ppub">1792-1074</issn>
<issn pub-type="epub">1792-1082</issn>
<publisher>
<publisher-name>D.A. Spandidos</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3892/ol.2023.13740</article-id>
<article-id pub-id-type="publisher-id">OL-25-4-13740</article-id>
<article-categories>
<subj-group>
<subject>Articles</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Pretreatment levels of serum alkaline phosphatase are associated with the prognosis of patients with non‑small cell lung cancer receiving immune checkpoint inhibitors</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author"><name><surname>Yang</surname><given-names>Tao</given-names></name>
<xref rid="af1-ol-25-4-13740" ref-type="aff">1</xref>
<xref rid="fn1-ol-25-4-13740" ref-type="author-notes">&#x002A;</xref></contrib>
<contrib contrib-type="author"><name><surname>Cheng</surname><given-names>Jia&#x0027;nan</given-names></name>
<xref rid="af2-ol-25-4-13740" ref-type="aff">2</xref>
<xref rid="fn1-ol-25-4-13740" ref-type="author-notes">&#x002A;</xref></contrib>
<contrib contrib-type="author"><name><surname>Fu</surname><given-names>Shihui</given-names></name>
<xref rid="af3-ol-25-4-13740" ref-type="aff">3</xref>
<xref rid="fn1-ol-25-4-13740" ref-type="author-notes">&#x002A;</xref></contrib>
<contrib contrib-type="author"><name><surname>Sun</surname><given-names>Tingting</given-names></name>
<xref rid="af4-ol-25-4-13740" ref-type="aff">4</xref></contrib>
<contrib contrib-type="author"><name><surname>Yang</surname><given-names>Kaidi</given-names></name>
<xref rid="af1-ol-25-4-13740" ref-type="aff">1</xref></contrib>
<contrib contrib-type="author"><name><surname>You</surname><given-names>Junhao</given-names></name>
<xref rid="af1-ol-25-4-13740" ref-type="aff">1</xref>
<xref rid="c1-ol-25-4-13740" ref-type="corresp"/></contrib>
<contrib contrib-type="author"><name><surname>Li</surname><given-names>Fang</given-names></name>
<xref rid="af1-ol-25-4-13740" ref-type="aff">1</xref>
<xref rid="c1-ol-25-4-13740" ref-type="corresp"/></contrib>
</contrib-group>
<aff id="af1-ol-25-4-13740"><label>1</label>Department of Oncology, Hainan Hospital of Chinese People&#x0027;s Liberation Army General Hospital, Sanya, Hainan 572013, P.R. China</aff>
<aff id="af2-ol-25-4-13740"><label>2</label>Institute of Cancer, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China</aff>
<aff id="af3-ol-25-4-13740"><label>3</label>Department of Cardiology, Hainan Hospital of Chinese People&#x0027;s Liberation Army General Hospital, Sanya, Hainan 572013, P.R. China</aff>
<aff id="af4-ol-25-4-13740"><label>4</label>Department of Orthopedics, Hainan Hospital of Chinese People&#x0027;s Liberation Army General Hospital, Sanya, Hainan 572013, P.R. China</aff>
<author-notes>
<corresp id="c1-ol-25-4-13740"><italic>Correspondence to</italic>: Dr Fang Li or Dr Junhao You, Department of Oncology, Hainan Hospital of Chinese People&#x0027;s Liberation Army General Hospital, 80 Jianglin Road, Haitang, Sanya, Hainan 572013, P.R. China, E-mail: <email>24103936@qq.com 422252147@qq.com </email></corresp>
<fn id="fn1-ol-25-4-13740"><label>&#x002A;</label><p>Contributed equally</p></fn></author-notes>
<pub-date pub-type="collection">
<month>04</month>
<year>2023</year></pub-date>
<pub-date pub-type="epub">
<day>03</day>
<month>03</month>
<year>2023</year></pub-date>
<volume>25</volume>
<issue>4</issue>
<elocation-id>154</elocation-id>
<history>
<date date-type="received"><day>21</day><month>08</month><year>2022</year></date>
<date date-type="accepted"><day>04</day><month>11</month><year>2022</year></date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2023, Spandidos Publications</copyright-statement>
<copyright-year>2023</copyright-year>
</permissions>
<abstract>
<p>Immune checkpoint inhibitors (ICIs) have been an encouraging treatment method in non-small cell lung cancer (NSCLC). However, bone and liver metastases are considered to restrain immunotherapy efficacy. Since serum alkaline phosphatase (ALP) is associated with bone and liver metastases, it was investigated whether serum ALP could be a novel biomarker to predict the efficacy of ICIs treatment. In the present study, 143 patients with NSCLC receiving ICIs treatment were retrospectively analyzed. The objective response rate (ORR) was compared between the ALP high and low groups, bone metastasis and non-bone metastasis groups, and liver metastasis or non-liver metastasis groups. The associations between clinical characteristics, including ALP level, bone or liver metastasis and median progression-free survival (mPFS) time were analyzed by univariate and multivariate Cox regression analysis. It was found that bone metastasis was associated with a lower ORR (24 vs. 43&#x0025;; P&#x003C;0.05) and shorter mPFS (10.2 vs. 17.3 months; P=0.010) in patients with NSCLC receiving ICIs. Liver metastasis was associated with lower ORR (22 vs. 38&#x0025;; P&#x003C;0.05), but not with mPFS (P=0.119). The ALP level was higher in patients with bone or liver metastasis than in those without (119.6 or 103.6 vs. 83.3 U/l, respectively; P&#x003C;0.05). Higher ALP levels were also associated with bone or liver metastasis, lower ORR (20 vs. 39&#x0025;; P&#x003C;0.05) and shorter mPFS (8.5 vs. 15.4 months; P=0.009). Cox regression analysis demonstrated that ALP was an independent prognostic indicator of mPFS (hazard ratio, 1.856; 95&#x0025; confidence interval, 1.030-3.343; P=0.040). In conclusion, pretreatment levels of serum ALP might be a predictive indicator of clinical outcome in patients with NSCLC after ICIs treatment.</p>
</abstract>
<kwd-group>
<kwd>ALP</kwd>
<kwd>biomarker</kwd>
<kwd>ICIs</kwd>
<kwd>NSCLC</kwd>
</kwd-group>
<funding-group>
<award-group>
<funding-source>National Nature Science Foundation of China</funding-source>
<award-id>82003006</award-id>
<award-id>82102878</award-id>
</award-group>
<award-group>
<funding-source>Nature Science Foundation of Hainan Province</funding-source>
<award-id>821QN384</award-id>
<award-id>818QN322</award-id>
</award-group>
<funding-statement>The study was supported by the National Nature Science Foundation of China (nos. 82003006 and 82102878) and Nature Science Foundation of Hainan Province (nos. 821QN384 and 818QN322).</funding-statement>
</funding-group>
</article-meta>
</front>
<body>
<sec sec-type="intro">
<title>Introduction</title>
<p>Lung cancer is the leading cause of cancer-related mortality worldwide (<xref rid="b1-ol-25-4-13740" ref-type="bibr">1</xref>). Non-small cell lung cancer (NSCLC) accounts for &#x007E;85&#x0025; of all histological types (<xref rid="b2-ol-25-4-13740" ref-type="bibr">2</xref>). The treatment plan for patients with advanced NSCLC depends on their genotype, and treatments include targeted therapy, chemotherapy and immunotherapy (<xref rid="b3-ol-25-4-13740" ref-type="bibr">3</xref>). Immune checkpoint inhibitors (ICIs), such as programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) or cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) antibodies, have been approved for the treatment of patients with advanced NSCLC based on their encouraging efficacy in a series of clinical trials (<xref rid="b4-ol-25-4-13740" ref-type="bibr">4</xref>,<xref rid="b5-ol-25-4-13740" ref-type="bibr">5</xref>). Although combination with chemotherapy or antiangiogenic agents improves the clinical outcome of ICIs, a considerable fraction of patients does not benefit from ICIs (<xref rid="b6-ol-25-4-13740" ref-type="bibr">6</xref>&#x2013;<xref rid="b8-ol-25-4-13740" ref-type="bibr">8</xref>). Therefore, it is important to identify biomarkers that can be used to predict the response to ICIs in patients with NSCLC.</p>
<p>At present, PD-L1 expression, tumor mutational burden (TMB) and microsatellite instability (MSI) status have been recognized as reliable indicators to predict the response to ICIs in NSCLC, hepatocellular carcinoma, urothelial carcinoma and other tumors (<xref rid="b9-ol-25-4-13740" ref-type="bibr">9</xref>,<xref rid="b10-ol-25-4-13740" ref-type="bibr">10</xref>). As the most important target of immunotherapy, the infiltration, T cell receptor repertoire diversity and gene signatures of CD8<sup>&#x002B;</sup> T cells can also predict the clinical benefit of ICIs treatment in advanced NSCLC (<xref rid="b11-ol-25-4-13740" ref-type="bibr">11</xref>&#x2013;<xref rid="b13-ol-25-4-13740" ref-type="bibr">13</xref>). Additionally, several routine blood parameters, including absolute eosinophil count (<xref rid="b14-ol-25-4-13740" ref-type="bibr">14</xref>), neutrophil-lymphocyte ratio (<xref rid="b15-ol-25-4-13740" ref-type="bibr">15</xref>) and lactate dehydrogenase levels (<xref rid="b16-ol-25-4-13740" ref-type="bibr">16</xref>), have been found to be valuable in the prediction of the clinical outcome of ICIs treatment. However, the role of serum alkaline phosphatase (ALP) in the prediction of ICIs treatment efficacy remains unclear.</p>
<p>ALP is a glycoprotein that catalyzes hydrolytic and phospho-transfer reactions. Elevated serum ALP has been reported in bone and liver-related diseases (<xref rid="b17-ol-25-4-13740" ref-type="bibr">17</xref>,<xref rid="b18-ol-25-4-13740" ref-type="bibr">18</xref>). Additionally, serum ALP has been found to be an independent prognostic factor in NSCLC, gastric cancer, breast cancer and other cancer types (<xref rid="b19-ol-25-4-13740" ref-type="bibr">19</xref>&#x2013;<xref rid="b21-ol-25-4-13740" ref-type="bibr">21</xref>). Furthermore, elevated ALP levels have been associated with bone or liver metastasis in patients with lung cancer, prostate cancer, breast cancer and other cancer types (<xref rid="b22-ol-25-4-13740" ref-type="bibr">22</xref>). In recent studies, bone and liver metastases have been reported to restrain immunotherapy efficacy via regulation of the tumor immune microenvironment (<xref rid="b23-ol-25-4-13740" ref-type="bibr">23</xref>,<xref rid="b24-ol-25-4-13740" ref-type="bibr">24</xref>). Therefore, an investigation was conducted to determine whether ALP could be a predictive indicator of ICIs treatment efficacy in patients with NSCLC.</p>
<p>In the present study it was found that bone or liver metastasis was associated with poor prognosis in patients with NSCLC receiving ICIs. Furthermore, elevated serum ALP levels were associated with bone and liver metastases, indicating that ALP levels might be an independent prognostic indicator of ICIs treatment efficacy in patients with NSCLC.</p>
</sec>
<sec sec-type="subjects|methods">
<title>Patients and methods</title>
<sec>
<title/>
<sec>
<title>Patients and data collection</title>
<p>Between January 2018 and December 2020, patients with NSCLC receiving ICIs treatment were investigated at the Institute of Cancer, Xinqiao Hospital, Third Military Medical University (Chongqing, China). Patients who met the following criteria were included in the present study: i) Pathologically diagnosed lung squamous cancer or adenocarcinoma without receiving an operation; ii) not harboring driver gene mutations, including EGFR, ALK, ROS1 and MET; iii) receiving ICIs treatment (including PD-1, PD-L1 or CTLA-4 antibody) for at least 2&#x2013;3 cycles (6 weeks); iv) complete image examination of evaluable foci pretreatment and post-treatment; and v) complete record of pretreatment ALP levels and complete record of follow-up. Patients with mutations of driver genes, or without records of pretreatment ALP levels, or receiving ICIs treatment &#x003C;6 weeks were excluded. Overall, 143 patients were included and data regarding their clinical characteristics [age, sex, histology type, TNM stage (according to the 8th AJCC staging system) (<xref rid="b25-ol-25-4-13740" ref-type="bibr">25</xref>), metastatic sites, treatment lines (first-line or &#x2265;2nd line) and treatment methods] were collected from medical records. The treatment methods included ICIs monotherapy or combined therapy with other treatments (chemotherapy, anti-angiogenic agents or both). The present study was approved by the Ethics Committee of Xinqiao Hospital, Third Military Medical University (approval no. AMUWEC20210386; Chongqing, China). All patients or their legal representatives gave written informed consent for the treatment and inquiries related to the present study.</p>
</sec>
<sec>
<title>ALP detection and cut-off value selection</title>
<p>ALP was detected using the endpoint spectrophotometric method in the peripheral blood of patients &#x003C;1 week before treatment with ICIs, and the ALP level data were collected from medical records. The normal level of ALP is between 0 and 110 U/l (<xref rid="b26-ol-25-4-13740" ref-type="bibr">26</xref>). In the present study, 110 U/l, which is the normal upper limit of ALP used at Xinqiao Hospital, was selected as the cut-off value to divide patients into high and low ALP level groups.</p>
</sec>
<sec>
<title>Follow-up evaluation and definition of progression-free survival (PFS)</title>
<p>Patients were evaluated during follow-up by CT of the lungs and abdomen or MRI of the brain. The response to ICIs treatment was classified according to iRECIST criteria (<xref rid="b27-ol-25-4-13740" ref-type="bibr">27</xref>) as complete response (iCR), partial response (iPR), stable disease or progressive disease. Treatment response was evaluated every 6 weeks.</p>
<p>The ORR was defined as the proportion of patients with response of iPR and iCR. PFS was defined as the time from the beginning of immunotherapy until recurrence of disease or death due to any cause. Telephone follow-up was performed every 6 months, and the last follow-up date was August 31, 2021.</p>
</sec>
<sec>
<title>Statistical analysis</title>
<p>The ALP level data are presented as the median and interquartile range. The mPFS data are presented as Kaplan-Meier curves. The composition of patients or response rate data are presented as n (&#x0025;), n or the proportion. The results of univariate and multivariate Cox regression analyses are presented as the hazard ratio and 95&#x0025; CI. The difference in ALP levels was analyzed using an unpaired Student&#x0027;s t-test or one-way ANOVA with a Bonferroni post hoc test. The associations between ALP levels and clinical characteristics were analyzed using a &#x03C7;<sup>2</sup> test and Fisher&#x0027;s exact test if the expected count was &#x003C;5. The percentages of clinical response of patients to ICIs treatment in two groups were compared using a &#x03C7;<sup>2</sup> test. Kaplan-Meier survival curves and the log-rank test were used to estimate mPFS, and univariate and multivariate Cox regression analyses were used to determine the associations between clinicopathological factors and survival. A forest plot was used to show the results of multivariate Cox regression analysis using Prism GraphPad 9.0 software (GraphPad Software, Inc.). All statistical analyses were conducted using SPSS 20.0 software (IBM Corp.). P&#x003C;0.05 was considered to indicate a statistically significant difference.</p>
</sec>
</sec>
</sec>
<sec sec-type="results">
<title>Results</title>
<sec>
<title/>
<sec>
<title>Patient characteristics</title>
<p>A total of 143 patients with NSCLC receiving ICIs were included, and their baseline characteristics are presented in <xref rid="tI-ol-25-4-13740" ref-type="table">Table I</xref>. There were 61 (42.7&#x0025;) older patients (age &#x2265;60 years), and the mean age was 57.26&#x00B1;9.86 years (range, 35&#x2013;76 years). Most patients were male (79.0&#x0025;) and had stage IV disease (87.4&#x0025;). In addition, 51.7&#x0025; of patients had squamous cancer, 59.4&#x0025; of patients received first-line ICIs treatment, and 45.5&#x0025; of patients were treated with combination therapy of ICIs and other treatments. The median follow-up time was 30.2 months (range, 2.7-52.4 months).</p>
</sec>
<sec>
<title>Bone and liver metastases predict poor prognosis of patients with NSCLC receiving ICIs</title>
<p>Previous preclinical and clinical evidence has demonstrated that bone or liver metastases can restrain immunotherapy efficacy (<xref rid="b23-ol-25-4-13740" ref-type="bibr">23</xref>,<xref rid="b24-ol-25-4-13740" ref-type="bibr">24</xref>). Therefore, the predictive value of bone or liver metastasis in the prognosis of patients with NSCLC receiving ICIs was investigated. There was a significant association between the response and bone metastasis (P&#x003C;0.05; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1A</xref>). Furthermore, bone metastasis was associated with a shorter mPFS time in patients with NSCLC receiving ICIs treatment (10.2 vs. 17.3 months; P=0.010; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1B</xref>). Similarly, there was also a significant association between the response and liver metastasis (P&#x003C;0.05; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1C</xref>). However, liver metastasis was not associated with mPFS time (P=0.119; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1D</xref>).</p>
</sec>
<sec>
<title>Elevated ALP levels are associated with bone and liver metastases in patients with NSCLC</title>
<p>ALP has been recognized as a valuable marker for skeletal and hepatobiliary disorders, including bone and liver metastases in patients with cancer (<xref rid="b22-ol-25-4-13740" ref-type="bibr">22</xref>). Therefore, the relationship between ALP levels and bone or liver metastasis in patients with NSCLC was investigated. ALP levels were higher in patients with bone or liver metastasis than in those without (119.6 or 103.6 vs. 83.3 U/l, respectively; P&#x003C;0.05; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1E</xref>). Furthermore, the ALP levels of patients with both bone and liver metastases were higher compared with the &#x2018;None&#x2019; group (135.7 vs. 83.3 U/l; P&#x003C;0.01; <xref rid="f1-ol-25-4-13740" ref-type="fig">Fig. 1E</xref>). In addition, higher levels of ALP were also associated with bone or liver metastasis, but not with age, sex, stage and other clinical characteristics (<xref rid="tII-ol-25-4-13740" ref-type="table">Table II</xref>).</p>
</sec>
<sec>
<title>Elevated ALP levels are an independent prognostic indicator for patients with NSCLC receiving ICIs</title>
<p>To determine the predictive value of ALP, the ALP levels in responders and non-responders to ICIs treatment were first compared. It was found that the levels of ALP were higher in non-responders than in responders (110.1 vs. 88.0 U/l; P&#x003C;0.01; <xref rid="f2-ol-25-4-13740" ref-type="fig">Fig. 2A</xref>). There was a significant association between the response and ALP levels (P&#x003C;0.05; <xref rid="f2-ol-25-4-13740" ref-type="fig">Fig. 2B</xref>). Furthermore, high ALP levels were associated with shorter mPFS (8.5 vs. 15.4 months; P=0.009; <xref rid="f2-ol-25-4-13740" ref-type="fig">Fig. 2C</xref>). Additionally, multivariate analysis revealed that ALP level, stage and histology type were independent prognostic indicators for mPFS in the present study (<xref rid="tIII-ol-25-4-13740" ref-type="table">Table III</xref>). Patients with high ALP levels or stage IV had a shorter mPFS than those with low ALP levels or stage III, while patients with squamous cancer had a longer mPFS than those with adenocarcinoma (<xref rid="f3-ol-25-4-13740" ref-type="fig">Fig. 3</xref>). However, associations between bone metastasis and mPFS were not observed in the multivariate analysis (<xref rid="tIII-ol-25-4-13740" ref-type="table">Table III</xref>).</p>
</sec>
</sec>
</sec>
<sec sec-type="discussion">
<title>Discussion</title>
<p>Immunotherapy, especially ICIs treatment, has been one of the most promising treatment approaches in NSCLC (<xref rid="b4-ol-25-4-13740" ref-type="bibr">4</xref>,<xref rid="b5-ol-25-4-13740" ref-type="bibr">5</xref>). ICIs monotherapy or combined therapy has been approved as a first-line treatment and has improved the prognosis of patients with advanced lung cancer (<xref rid="b28-ol-25-4-13740" ref-type="bibr">28</xref>,<xref rid="b29-ol-25-4-13740" ref-type="bibr">29</xref>). Although the ORR has been increased by combined therapy independent of the PD-L1 level measured, not all patients benefit from the ICIs treatment, and this is termed a so-called primary resistance (<xref rid="b30-ol-25-4-13740" ref-type="bibr">30</xref>).</p>
<p>Numerous studies have demonstrated the mechanisms of primary resistance in ICIs treatment (<xref rid="b31-ol-25-4-13740" ref-type="bibr">31</xref>&#x2013;<xref rid="b33-ol-25-4-13740" ref-type="bibr">33</xref>), which include the absence of tumor-specific antigens, downregulation of antigen presentation molecules and suppression of T cell infiltration. Emerging evidence has indicated that bone and liver metastases might induce primary resistance to immunotherapy by regulating the immune microenvironment (<xref rid="b23-ol-25-4-13740" ref-type="bibr">23</xref>,<xref rid="b24-ol-25-4-13740" ref-type="bibr">24</xref>). Subgroup analysis of clinical trials revealed that patients with prostate cancer and bone metastasis exhibited primary resistance to ICIs treatment (<xref rid="b34-ol-25-4-13740" ref-type="bibr">34</xref>). Mechanistically, bone metastatic loci could release TGF-&#x03B2; to restrain Th1 lineage development to further inhibit antitumor immunity (<xref rid="b34-ol-25-4-13740" ref-type="bibr">34</xref>). Furthermore, a recent study reported that the presence of liver metastasis is associated with poor response to immunotherapy in patients with melanoma or NSCLC, which is consistent with the findings of the present study (<xref rid="b23-ol-25-4-13740" ref-type="bibr">23</xref>). An animal experiment revealed that liver metastasis could recruit immunosuppressive macrophages to promote antigen-specific T cell apoptosis, resulting in a systemic loss of T cells and diminished immunotherapy efficacy (<xref rid="b23-ol-25-4-13740" ref-type="bibr">23</xref>). However, a recent meta-analysis reported that patients with lung cancer with and without liver metastasis obtained comparable efficacy after ICIs treatment (<xref rid="b35-ol-25-4-13740" ref-type="bibr">35</xref>). Therefore, prospective studies might be required to further identify the relationship between liver metastasis and the efficacy of ICIs treatment.</p>
<p>Primary resistance cannot be completely explained by currently recognized biomarkers, such as PD-L1 expression, MSI status or TMB level. Thus, studies are increasingly focusing on other biomarkers to predict the response to ICIs treatment (<xref rid="b14-ol-25-4-13740" ref-type="bibr">14</xref>,<xref rid="b36-ol-25-4-13740" ref-type="bibr">36</xref>). As aforementioned, elevated serum ALP levels have been demonstrated to be associated with bone and liver-related diseases. In the present study, it was found that high levels of serum ALP were associated with bone or liver metastasis in patients with NSCLC, which is consistent with previous studies (<xref rid="b22-ol-25-4-13740" ref-type="bibr">22</xref>,<xref rid="b37-ol-25-4-13740" ref-type="bibr">37</xref>). Although numerous studies have demonstrated that a high ALP level predicted poor prognosis in various types of cancer, such as NSCLC, gastric cancer and breast cancer (<xref rid="b19-ol-25-4-13740" ref-type="bibr">19</xref>&#x2013;<xref rid="b21-ol-25-4-13740" ref-type="bibr">21</xref>), there is little research on the relationship between serum ALP levels and efficacy of ICIs treatment. In the present study, serum ALP levels were identified as an independent prognostic indicator of ICIs treatment in patients with NSCLC. Recently, it was also reported that high levels of serum ALP predicted poor prognosis in patients with HER-2-negative gastric cancer receiving immunotherapy (<xref rid="b38-ol-25-4-13740" ref-type="bibr">38</xref>), which might support the findings of the present study. However, the cut-off value of ALP was not the same in the previous study and the present study (225 U/l in the previous study and 110U/l in the present study). The cut-off value in the present study was based on the normal upper limit of ALP, and was consistent with another study (<xref rid="b26-ol-25-4-13740" ref-type="bibr">26</xref>). Therefore, 110 U/l might be a more suitable cut-off value. There are four isoenzymes of ALP in human serum, including tissue non-specific, germ cell, placental and intestinal ALP, but the standard test could not detect the tissue non-specific isoenzymes, which account for 26&#x2013;34&#x0025; of total ALP (<xref rid="b22-ol-25-4-13740" ref-type="bibr">22</xref>). Thus, whether the undetectable isoenzymes of ALP could also predict the efficacy of ICIs treatment remains to be further studied.</p>
<p>As aforementioned, bone or liver metastasis, and high ALP levels were associated with poor prognosis in patients with NSCLC receiving ICIs treatment in the present study. However, in the present study, it was found that only high ALP levels, rather than bone or liver metastasis, were an independent prognostic factor using multivariate analysis, rather than bone or liver metastasis. This difference indicated that other factors affecting ALP levels, such as benign liver and bone diseases, might also restrain the efficacy of ICIs treatment. Furthermore, it was found that higher ALP levels were associated with a shorter PFS time in patients without bone metastasis (data not shown). However, this hypothesis should be verified in further studies.</p>
<p>There were a number of limitations in the present study. Firstly, this was a retrospective study in a single center with a small number of cases. Secondly, the lack of overall survival data might affect the reliability of the conclusions made. Thirdly, the PD-L1 expression, TMB and MSI status in patients might also affect the outcomes of ICIs treatment (<xref rid="b9-ol-25-4-13740" ref-type="bibr">9</xref>,<xref rid="b10-ol-25-4-13740" ref-type="bibr">10</xref>), which should be explored further in the future.</p>
<p>In conclusion, serum ALP levels might be an independent predictor of the response to ICIs treatment in patients with NSCLC. Due to a number of limitations of the present study, prospective studies are required to determine the actual prognostic significance of ALP levels in patients with NSCLC.</p>
</sec>
</body>
<back>
<ack>
<title>Acknowledgements</title>
<p>Not applicable.</p>
</ack>
<sec sec-type="data-availability">
<title>Availability of data and materials</title>
<p>The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.</p>
</sec>
<sec>
<title>Authors&#x0027; contributions</title>
<p>FL and JY conceived and designed the study. KY and TS developed the methodology. TY, JC and SF acquired the data. TY and JC confirmed the authenticity of all the raw data. TY and JC analyzed and interpreted the data. TY and JC wrote the original draft. JY and FL reviewed and revised the manuscript. FL and JY supervised the study. TY, JC and TS were involved in funding acquisition. All authors read and approved the final manuscript.</p>
</sec>
<sec>
<title>Ethics approval and consent to participate</title>
<p>The study was approved by the Ethics Committee of Xinqiao Hospital, Third Military Medical University (Chongqing, China). All patients or their legal representatives gave written informed consent for the treatment and inquiries related to this study.</p>
</sec>
<sec>
<title>Patient consent for publication</title>
<p>The patients provided written informed consent for publication of any associated data.</p>
</sec>
<sec sec-type="COI-statement">
<title>Competing interests</title>
<p>The authors declare that they have no competing interests.</p>
</sec>
<glossary>
<def-list>
<title>Abbreviations</title>
<def-item><term>ALP</term><def><p>alkaline phosphatase</p></def></def-item>
<def-item><term>CTLA-4</term><def><p>cytotoxic T lymphocyte-associated antigen-4</p></def></def-item>
<def-item><term>ICIs</term><def><p>immune checkpoint inhibitors</p></def></def-item>
<def-item><term>MSI</term><def><p>microsatellite instability</p></def></def-item>
<def-item><term>NSCLC</term><def><p>non-small cell lung cancer</p></def></def-item>
<def-item><term>ORR</term><def><p>objective response rate</p></def></def-item>
<def-item><term>PD-1</term><def><p>programmed cell death-1</p></def></def-item>
<def-item><term>PD-L1</term><def><p>programmed cell death-ligand 1</p></def></def-item>
<def-item><term>PFS</term><def><p>progression-free survival</p></def></def-item>
<def-item><term>TMB</term><def><p>tumor mutational burden</p></def></def-item>
</def-list>
</glossary>
<ref-list>
<title>References</title>
<ref id="b1-ol-25-4-13740"><label>1</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Barta</surname><given-names>JA</given-names></name><name><surname>Powell</surname><given-names>CA</given-names></name><name><surname>Wisnivesky</surname><given-names>JP</given-names></name></person-group><article-title>Global epidemiology of lung cancer</article-title><source>Ann Glob Health</source><volume>85</volume><fpage>8</fpage><year>2019</year><pub-id pub-id-type="doi">10.5334/aogh.2419</pub-id><pub-id pub-id-type="pmid">30741509</pub-id></element-citation></ref>
<ref id="b2-ol-25-4-13740"><label>2</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Molina</surname><given-names>JR</given-names></name><name><surname>Yang</surname><given-names>P</given-names></name><name><surname>Cassivi</surname><given-names>SD</given-names></name><name><surname>Schild</surname><given-names>SE</given-names></name><name><surname>Adjei</surname><given-names>AA</given-names></name></person-group><article-title>Non-small cell lung cancer: Epidemiology, risk factors, treatment, and survivorship</article-title><source>Mayo Clin Proc</source><volume>83</volume><fpage>584</fpage><lpage>594</lpage><year>2008</year><pub-id pub-id-type="doi">10.4065/83.5.584</pub-id><pub-id pub-id-type="pmid">18452692</pub-id></element-citation></ref>
<ref id="b3-ol-25-4-13740"><label>3</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Li</surname><given-names>T</given-names></name><name><surname>Kung</surname><given-names>HJ</given-names></name><name><surname>Mack</surname><given-names>PC</given-names></name><name><surname>Gandara</surname><given-names>DR</given-names></name></person-group><article-title>Genotyping and genomic profiling of non-small-cell lung cancer: Implications for current and future therapies</article-title><source>J Clin Oncol</source><volume>31</volume><fpage>1039</fpage><lpage>1049</lpage><year>2013</year><pub-id pub-id-type="doi">10.1200/JCO.2012.45.3753</pub-id><pub-id pub-id-type="pmid">23401433</pub-id></element-citation></ref>
<ref id="b4-ol-25-4-13740"><label>4</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Socinski</surname><given-names>MA</given-names></name><name><surname>Jotte</surname><given-names>RM</given-names></name><name><surname>Cappuzzo</surname><given-names>F</given-names></name><name><surname>Orlandi</surname><given-names>F</given-names></name><name><surname>Stroyakovskiy</surname><given-names>D</given-names></name><name><surname>Nogami</surname><given-names>N</given-names></name><name><surname>Rodr&#x00ED;guez-Abreu</surname><given-names>D</given-names></name><name><surname>Moro-Sibilot</surname><given-names>D</given-names></name><name><surname>Thomas</surname><given-names>CA</given-names></name><name><surname>Barlesi</surname><given-names>F</given-names></name><etal/></person-group><article-title>Atezolizumab for First-Line Treatment of Metastatic Nonsquamous NSCLC</article-title><source>N Engl J Med</source><volume>378</volume><fpage>2288</fpage><lpage>2301</lpage><year>2018</year><pub-id pub-id-type="doi">10.1056/NEJMoa1716948</pub-id><pub-id pub-id-type="pmid">29863955</pub-id></element-citation></ref>
<ref id="b5-ol-25-4-13740"><label>5</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Reck</surname><given-names>M</given-names></name><name><surname>Rodriguez-Abreu</surname><given-names>D</given-names></name><name><surname>Robinson</surname><given-names>AG</given-names></name><name><surname>Hui</surname><given-names>R</given-names></name><name><surname>Cs&#x0151;szi</surname><given-names>T</given-names></name><name><surname>F&#x00FC;l&#x00F6;p</surname><given-names>A</given-names></name><name><surname>Gottfried</surname><given-names>M</given-names></name><name><surname>Peled</surname><given-names>N</given-names></name><name><surname>Tafreshi</surname><given-names>A</given-names></name><name><surname>Cuffe</surname><given-names>S</given-names></name><etal/></person-group><article-title>Updated analysis of KEYNOTE-024: Pembrolizumab versus platinum-based chemotherapy for advanced non-small-cell lung cancer with PD-L1 tumor proportion score of 50&#x0025; or greater</article-title><source>J Clin Oncol</source><volume>37</volume><fpage>537</fpage><lpage>546</lpage><year>2019</year><pub-id pub-id-type="doi">10.1200/JCO.18.00149</pub-id><pub-id pub-id-type="pmid">30620668</pub-id></element-citation></ref>
<ref id="b6-ol-25-4-13740"><label>6</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Rodriguez-Abreu</surname><given-names>D</given-names></name><name><surname>Powell</surname><given-names>SF</given-names></name><name><surname>Hochmair</surname><given-names>MJ</given-names></name><name><surname>Gadgeel</surname><given-names>S</given-names></name><name><surname>Esteban</surname><given-names>E</given-names></name><name><surname>Felip</surname><given-names>E</given-names></name><name><surname>Speranza</surname><given-names>G</given-names></name><name><surname>De Angelis</surname><given-names>F</given-names></name><name><surname>D&#x00F3;mine</surname><given-names>M</given-names></name><name><surname>Cheng</surname><given-names>SY</given-names></name><etal/></person-group><article-title>Pemetrexed plus platinum with or without pembrolizumab in patients with previously untreated metastatic nonsquamous NSCLC: Protocol-specified final analysis from KEYNOTE-189</article-title><source>Ann Oncol</source><volume>32</volume><fpage>881</fpage><lpage>895</lpage><year>2021</year><pub-id pub-id-type="doi">10.1016/j.annonc.2021.04.008</pub-id><pub-id pub-id-type="pmid">33894335</pub-id></element-citation></ref>
<ref id="b7-ol-25-4-13740"><label>7</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Paz-Ares</surname><given-names>L</given-names></name><name><surname>Vicente</surname><given-names>D</given-names></name><name><surname>Tafreshi</surname><given-names>A</given-names></name><name><surname>Robinson</surname><given-names>A</given-names></name><name><surname>Soto Parra</surname><given-names>H</given-names></name><name><surname>Mazi&#x00E8;res</surname><given-names>J</given-names></name><name><surname>Hermes</surname><given-names>B</given-names></name><name><surname>Cicin</surname><given-names>I</given-names></name><name><surname>Medgyasszay</surname><given-names>B</given-names></name><name><surname>Rodr&#x00ED;guez-Cid</surname><given-names>J</given-names></name><etal/></person-group><article-title>A randomized, placebo-controlled trial of pembrolizumab plus chemotherapy in patients with metastatic squamous NSCLC: Protocol-Specified final analysis of KEYNOTE-407</article-title><source>J Thorac Oncol</source><volume>15</volume><fpage>1657</fpage><lpage>1669</lpage><year>2020</year><pub-id pub-id-type="doi">10.1016/j.jtho.2020.06.015</pub-id><pub-id pub-id-type="pmid">32599071</pub-id></element-citation></ref>
<ref id="b8-ol-25-4-13740"><label>8</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Socinski</surname><given-names>MA</given-names></name><name><surname>Nishio</surname><given-names>M</given-names></name><name><surname>Jotte</surname><given-names>RM</given-names></name><name><surname>Cappuzzo</surname><given-names>F</given-names></name><name><surname>Orlandi</surname><given-names>F</given-names></name><name><surname>Stroyakovskiy</surname><given-names>D</given-names></name><name><surname>Nogami</surname><given-names>N</given-names></name><name><surname>Rodr&#x00ED;guez-Abreu</surname><given-names>D</given-names></name><name><surname>Moro-Sibilot</surname><given-names>D</given-names></name><name><surname>Thomas</surname><given-names>CA</given-names></name><etal/></person-group><article-title>IMpower150 final overall survival analyses for atezolizumab plus bevacizumab and chemotherapy in first-line metastatic nonsquamous NSCLC</article-title><source>J Thorac Oncol</source><volume>16</volume><fpage>1909</fpage><lpage>1924</lpage><year>2021</year><pub-id pub-id-type="doi">10.1016/j.jtho.2021.07.009</pub-id><pub-id pub-id-type="pmid">34311108</pub-id></element-citation></ref>
<ref id="b9-ol-25-4-13740"><label>9</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Yarchoan</surname><given-names>M</given-names></name><name><surname>Albacker</surname><given-names>LA</given-names></name><name><surname>Hopkins</surname><given-names>AC</given-names></name><name><surname>Montesion</surname><given-names>M</given-names></name><name><surname>Murugesan</surname><given-names>K</given-names></name><name><surname>Vithayathil</surname><given-names>TT</given-names></name><name><surname>Zaidi</surname><given-names>N</given-names></name><name><surname>Azad</surname><given-names>NS</given-names></name><name><surname>Laheru</surname><given-names>DA</given-names></name><name><surname>Frampton</surname><given-names>GM</given-names></name><name><surname>Jaffee</surname><given-names>EM</given-names></name></person-group><article-title>PD-L1 expression and tumor mutational burden are independent biomarkers in most cancers</article-title><source>JCI Insight</source><volume>4</volume><fpage>e126908</fpage><year>2019</year><pub-id pub-id-type="doi">10.1172/jci.insight.126908</pub-id><pub-id pub-id-type="pmid">30895946</pub-id></element-citation></ref>
<ref id="b10-ol-25-4-13740"><label>10</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chang</surname><given-names>L</given-names></name><name><surname>Chang</surname><given-names>M</given-names></name><name><surname>Chang</surname><given-names>HM</given-names></name><name><surname>Chang</surname><given-names>F</given-names></name></person-group><article-title>Microsatellite instability: A predictive biomarker for cancer immunotherapy</article-title><source>Appl Immunohistochem Mol Morphol</source><volume>26</volume><fpage>e15</fpage><lpage>e21</lpage><year>2018</year><pub-id pub-id-type="doi">10.1097/PAI.0000000000000575</pub-id><pub-id pub-id-type="pmid">28877075</pub-id></element-citation></ref>
<ref id="b11-ol-25-4-13740"><label>11</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jiang</surname><given-names>P</given-names></name><name><surname>Gu</surname><given-names>S</given-names></name><name><surname>Pan</surname><given-names>D</given-names></name><name><surname>Fu</surname><given-names>J</given-names></name><name><surname>Sahu</surname><given-names>A</given-names></name><name><surname>Hu</surname><given-names>X</given-names></name><name><surname>Li</surname><given-names>Z</given-names></name><name><surname>Traugh</surname><given-names>N</given-names></name><name><surname>Bu</surname><given-names>X</given-names></name><name><surname>Li</surname><given-names>B</given-names></name><etal/></person-group><article-title>Signatures of T cell dysfunction and exclusion predict cancer immunotherapy response</article-title><source>Nat Med</source><volume>24</volume><fpage>1550</fpage><lpage>1558</lpage><year>2018</year><pub-id pub-id-type="doi">10.1038/s41591-018-0136-1</pub-id><pub-id pub-id-type="pmid">30127393</pub-id></element-citation></ref>
<ref id="b12-ol-25-4-13740"><label>12</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Hurkmans</surname><given-names>DP</given-names></name><name><surname>Kuipers</surname><given-names>ME</given-names></name><name><surname>Smit</surname><given-names>J</given-names></name><name><surname>van Marion</surname><given-names>R</given-names></name><name><surname>Mathijssen</surname><given-names>RHJ</given-names></name><name><surname>Postmus</surname><given-names>PE</given-names></name><name><surname>Hiemstra</surname><given-names>PS</given-names></name><name><surname>Aerts</surname><given-names>JGJV</given-names></name><name><surname>von der Th&#x00FC;sen</surname><given-names>JH</given-names></name><name><surname>van der Burg</surname><given-names>SH</given-names></name></person-group><article-title>Tumor mutational load, CD8(&#x002B;) T cells, expression of PD-L1 and HLA class I to guide immunotherapy decisions in NSCLC patients</article-title><source>Cancer Immunol Immunother</source><volume>69</volume><fpage>771</fpage><lpage>777</lpage><year>2020</year><pub-id pub-id-type="doi">10.1007/s00262-020-02506-x</pub-id><pub-id pub-id-type="pmid">32047958</pub-id></element-citation></ref>
<ref id="b13-ol-25-4-13740"><label>13</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Han</surname><given-names>J</given-names></name><name><surname>Duan</surname><given-names>J</given-names></name><name><surname>Bai</surname><given-names>H</given-names></name><name><surname>Wang</surname><given-names>Y</given-names></name><name><surname>Wan</surname><given-names>R</given-names></name><name><surname>Wang</surname><given-names>X</given-names></name><name><surname>Chen</surname><given-names>S</given-names></name><name><surname>Tian</surname><given-names>Y</given-names></name><name><surname>Wang</surname><given-names>D</given-names></name><name><surname>Fei</surname><given-names>K</given-names></name><etal/></person-group><article-title>TCR repertoire diversity of peripheral PD-1(&#x002B;)CD8(&#x002B;) T cells predicts clinical outcomes after immunotherapy in patients with non-small cell lung cancer</article-title><source>Cancer Immunol Res</source><volume>8</volume><fpage>146</fpage><lpage>154</lpage><year>2020</year><pub-id pub-id-type="doi">10.1158/2326-6066.CIR-19-0398</pub-id><pub-id pub-id-type="pmid">31719056</pub-id></element-citation></ref>
<ref id="b14-ol-25-4-13740"><label>14</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Soyano</surname><given-names>AE</given-names></name><name><surname>Dholaria</surname><given-names>B</given-names></name><name><surname>Marin-Acevedo</surname><given-names>JA</given-names></name><name><surname>Diehl</surname><given-names>N</given-names></name><name><surname>Hodge</surname><given-names>D</given-names></name><name><surname>Luo</surname><given-names>Y</given-names></name><name><surname>Manochakian</surname><given-names>R</given-names></name><name><surname>Chumsri</surname><given-names>S</given-names></name><name><surname>Adjei</surname><given-names>A</given-names></name><name><surname>Knutson</surname><given-names>KL</given-names></name><name><surname>Lou</surname><given-names>Y</given-names></name></person-group><article-title>Peripheral blood biomarkers correlate with outcomes in advanced non-small cell lung Cancer patients treated with anti-PD-1 antibodies</article-title><source>J Immunother Cancer</source><volume>6</volume><fpage>129</fpage><year>2018</year><pub-id pub-id-type="doi">10.1186/s40425-018-0447-2</pub-id><pub-id pub-id-type="pmid">30470260</pub-id></element-citation></ref>
<ref id="b15-ol-25-4-13740"><label>15</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Diem</surname><given-names>S</given-names></name><name><surname>Schmid</surname><given-names>S</given-names></name><name><surname>Krapf</surname><given-names>M</given-names></name><name><surname>Flatz</surname><given-names>L</given-names></name><name><surname>Born</surname><given-names>D</given-names></name><name><surname>Jochum</surname><given-names>W</given-names></name><name><surname>Templeton</surname><given-names>AJ</given-names></name><name><surname>Fr&#x00FC;h</surname><given-names>M</given-names></name></person-group><article-title>Neutrophil-to-Lymphocyte ratio (NLR) and Platelet-to-Lymphocyte ratio (PLR) as prognostic markers in patients with non-small cell lung cancer (NSCLC) treated with nivolumab</article-title><source>Lung Cancer</source><volume>111</volume><fpage>176</fpage><lpage>181</lpage><year>2017</year><pub-id pub-id-type="doi">10.1016/j.lungcan.2017.07.024</pub-id><pub-id pub-id-type="pmid">28838390</pub-id></element-citation></ref>
<ref id="b16-ol-25-4-13740"><label>16</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Banna</surname><given-names>GL</given-names></name><name><surname>Signorelli</surname><given-names>D</given-names></name><name><surname>Metro</surname><given-names>G</given-names></name><name><surname>Galetta</surname><given-names>D</given-names></name><name><surname>De Toma</surname><given-names>A</given-names></name><name><surname>Cantale</surname><given-names>O</given-names></name><name><surname>Banini</surname><given-names>M</given-names></name><name><surname>Friedlaender</surname><given-names>A</given-names></name><name><surname>Pizzutillo</surname><given-names>P</given-names></name><name><surname>Garassino</surname><given-names>MC</given-names></name><name><surname>Addeo</surname><given-names>A</given-names></name></person-group><article-title>Neutrophil-to-lymphocyte ratio in combination with PD-L1 or lactate dehydrogenase as biomarkers for high PD-L1 non-small cell lung cancer treated with first-line pembrolizumab</article-title><source>Transl Lung Cancer Res</source><volume>9</volume><fpage>1533</fpage><lpage>1542</lpage><year>2020</year><pub-id pub-id-type="doi">10.21037/tlcr-19-583</pub-id><pub-id pub-id-type="pmid">32953525</pub-id></element-citation></ref>
<ref id="b17-ol-25-4-13740"><label>17</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Siddique</surname><given-names>A</given-names></name><name><surname>Kowdley</surname><given-names>KV</given-names></name></person-group><article-title>Approach to a patient with elevated serum alkaline phosphatase</article-title><source>Clin Liver Dis</source><volume>16</volume><fpage>199</fpage><lpage>229</lpage><year>2012</year><pub-id pub-id-type="doi">10.1016/j.cld.2012.03.012</pub-id><pub-id pub-id-type="pmid">22541695</pub-id></element-citation></ref>
<ref id="b18-ol-25-4-13740"><label>18</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Vimalraj</surname><given-names>S</given-names></name></person-group><article-title>Alkaline phosphatase: Structure, expression and its function in bone mineralization</article-title><source>Gene</source><volume>754</volume><fpage>144855</fpage><year>2020</year><pub-id pub-id-type="doi">10.1016/j.gene.2020.144855</pub-id><pub-id pub-id-type="pmid">32522695</pub-id></element-citation></ref>
<ref id="b19-ol-25-4-13740"><label>19</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Namikawa</surname><given-names>T</given-names></name><name><surname>Ishida</surname><given-names>N</given-names></name><name><surname>Tsuda</surname><given-names>S</given-names></name><name><surname>Fujisawa</surname><given-names>K</given-names></name><name><surname>Munekage</surname><given-names>E</given-names></name><name><surname>Iwabu</surname><given-names>J</given-names></name><name><surname>Munekage</surname><given-names>M</given-names></name><name><surname>Uemura</surname><given-names>S</given-names></name><name><surname>Tsujii</surname><given-names>S</given-names></name><name><surname>Tamura</surname><given-names>T</given-names></name><etal/></person-group><article-title>Prognostic significance of serum alkaline phosphatase and lactate dehydrogenase levels in patients with unresectable advanced gastric cancer</article-title><source>Gastric Cancer</source><volume>22</volume><fpage>684</fpage><lpage>691</lpage><year>2019</year><pub-id pub-id-type="doi">10.1007/s10120-018-0897-8</pub-id><pub-id pub-id-type="pmid">30417313</pub-id></element-citation></ref>
<ref id="b20-ol-25-4-13740"><label>20</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Chen</surname><given-names>B</given-names></name><name><surname>Dai</surname><given-names>D</given-names></name><name><surname>Tang</surname><given-names>H</given-names></name><name><surname>Chen</surname><given-names>X</given-names></name><name><surname>Ai</surname><given-names>X</given-names></name><name><surname>Huang</surname><given-names>X</given-names></name><name><surname>Wei</surname><given-names>W</given-names></name><name><surname>Xie</surname><given-names>X</given-names></name></person-group><article-title>Pre-treatment serum alkaline phosphatase and lactate dehydrogenase as prognostic factors in triple negative breast cancer</article-title><source>J Cancer</source><volume>7</volume><fpage>2309</fpage><lpage>2316</lpage><year>2016</year><pub-id pub-id-type="doi">10.7150/jca.16622</pub-id><pub-id pub-id-type="pmid">27994669</pub-id></element-citation></ref>
<ref id="b21-ol-25-4-13740"><label>21</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Li</surname><given-names>D</given-names></name><name><surname>Yu</surname><given-names>H</given-names></name><name><surname>Li</surname><given-names>W</given-names></name></person-group><article-title>Albumin-to-alkaline phosphatase ratio at diagnosis predicts survival in patients with metastatic non-small-cell lung cancer</article-title><source>Onco Targets Ther</source><volume>12</volume><fpage>5241</fpage><lpage>5249</lpage><year>2019</year><pub-id pub-id-type="doi">10.2147/OTT.S203321</pub-id><pub-id pub-id-type="pmid">31303770</pub-id></element-citation></ref>
<ref id="b22-ol-25-4-13740"><label>22</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>&#x00D0;okic-Lisanin</surname><given-names>M</given-names></name><name><surname>Pantovic</surname><given-names>V</given-names></name><name><surname>Jovanovic</surname><given-names>Z</given-names></name><name><surname>Samardz</surname><given-names>G</given-names></name><name><surname>Jurisic</surname><given-names>V</given-names></name></person-group><article-title>Values of alkaline phosphathase and their isoenzyme profiles in patients with cancer in respect to bone and liver metastasis</article-title><source>Arch Oncol</source><volume>21</volume><fpage>14</fpage><lpage>16</lpage><year>2013</year><pub-id pub-id-type="doi">10.2298/AOO1301014D</pub-id></element-citation></ref>
<ref id="b23-ol-25-4-13740"><label>23</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Yu</surname><given-names>J</given-names></name><name><surname>Green</surname><given-names>MD</given-names></name><name><surname>Li</surname><given-names>S</given-names></name><name><surname>Sun</surname><given-names>Y</given-names></name><name><surname>Journey</surname><given-names>SN</given-names></name><name><surname>Choi</surname><given-names>JE</given-names></name><name><surname>Rizvi</surname><given-names>SM</given-names></name><name><surname>Qin</surname><given-names>A</given-names></name><name><surname>Waninger</surname><given-names>JJ</given-names></name><name><surname>Lang</surname><given-names>X</given-names></name><etal/></person-group><article-title>Liver metastasis restrains immunotherapy efficacy via macrophage-mediated T cell elimination</article-title><source>Nat Med</source><volume>27</volume><fpage>152</fpage><lpage>164</lpage><year>2021</year><pub-id pub-id-type="doi">10.1038/s41591-020-1131-x</pub-id><pub-id pub-id-type="pmid">33398162</pub-id></element-citation></ref>
<ref id="b24-ol-25-4-13740"><label>24</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Landi</surname><given-names>L</given-names></name><name><surname>D&#x0027;Inca</surname><given-names>F</given-names></name><name><surname>Gelibter</surname><given-names>A</given-names></name><name><surname>Chiari</surname><given-names>R</given-names></name><name><surname>Grossi</surname><given-names>F</given-names></name><name><surname>Delmonte</surname><given-names>A</given-names></name><name><surname>Passaro</surname><given-names>A</given-names></name><name><surname>Signorelli</surname><given-names>D</given-names></name><name><surname>Gelsomino</surname><given-names>F</given-names></name><name><surname>Galetta</surname><given-names>D</given-names></name><etal/></person-group><article-title>Bone metastases and immunotherapy in patients with advanced non-small-cell lung cancer</article-title><source>J Immunother Cancer</source><volume>7</volume><fpage>316</fpage><year>2019</year><pub-id pub-id-type="doi">10.1186/s40425-019-0793-8</pub-id><pub-id pub-id-type="pmid">31752994</pub-id></element-citation></ref>
<ref id="b25-ol-25-4-13740"><label>25</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Detterbeck</surname><given-names>FC</given-names></name><name><surname>Boffa</surname><given-names>DJ</given-names></name><name><surname>Kim</surname><given-names>AW</given-names></name><name><surname>Tanoue</surname><given-names>LT</given-names></name></person-group><article-title>The eighth edition lung cancer stage classification</article-title><source>Chest</source><volume>151</volume><fpage>193</fpage><lpage>203</lpage><year>2017</year><pub-id pub-id-type="doi">10.1016/j.chest.2016.10.010</pub-id><pub-id pub-id-type="pmid">27780786</pub-id></element-citation></ref>
<ref id="b26-ol-25-4-13740"><label>26</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>He</surname><given-names>S</given-names></name><name><surname>Wang</surname><given-names>Y</given-names></name><name><surname>Peng</surname><given-names>H</given-names></name><name><surname>Yang</surname><given-names>L</given-names></name><name><surname>Chen</surname><given-names>H</given-names></name><name><surname>Liang</surname><given-names>S</given-names></name><name><surname>Lu</surname><given-names>L</given-names></name><name><surname>Chen</surname><given-names>Y</given-names></name></person-group><article-title>Pretreatment alkaline phosphatase and epstein-barr virus DNA predict poor prognosis and response to salvage radiotherapy in patients with nasopharyngeal carcinoma and metachronous bone-only metastasis</article-title><source>J Cancer</source><volume>8</volume><fpage>417</fpage><lpage>424</lpage><year>2017</year><pub-id pub-id-type="doi">10.7150/jca.17310</pub-id><pub-id pub-id-type="pmid">28261343</pub-id></element-citation></ref>
<ref id="b27-ol-25-4-13740"><label>27</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Seymour</surname><given-names>L</given-names></name><name><surname>Bogaerts</surname><given-names>J</given-names></name><name><surname>Perrone</surname><given-names>A</given-names></name><name><surname>Ford</surname><given-names>R</given-names></name><name><surname>Schwartz</surname><given-names>LH</given-names></name><name><surname>Mandrekar</surname><given-names>S</given-names></name><name><surname>Lin</surname><given-names>NU</given-names></name><name><surname>Liti&#x00E8;re</surname><given-names>S</given-names></name><name><surname>Dancey</surname><given-names>J</given-names></name><name><surname>Chen</surname><given-names>A</given-names></name><etal/></person-group><article-title>iRECIST: Guidelines for response criteria for use in trials testing immunotherapeutics</article-title><source>Lancet Oncol</source><volume>18</volume><fpage>e143</fpage><lpage>e152</lpage><year>2017</year><pub-id pub-id-type="doi">10.1016/S1470-2045(17)30074-8</pub-id><pub-id pub-id-type="pmid">28271869</pub-id></element-citation></ref>
<ref id="b28-ol-25-4-13740"><label>28</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Pai-Scherf</surname><given-names>L</given-names></name><name><surname>Blumenthal</surname><given-names>GM</given-names></name><name><surname>Li</surname><given-names>H</given-names></name><name><surname>Subramaniam</surname><given-names>S</given-names></name><name><surname>Mishra-Kalyani</surname><given-names>PS</given-names></name><name><surname>He</surname><given-names>K</given-names></name><name><surname>Zhao</surname><given-names>H</given-names></name><name><surname>Yu</surname><given-names>J</given-names></name><name><surname>Paciga</surname><given-names>M</given-names></name><name><surname>Goldberg</surname><given-names>KB</given-names></name><etal/></person-group><article-title>FDA Approval Summary: Pembrolizumab for treatment of metastatic non-small cell lung cancer: First-Line therapy and beyond</article-title><source>Oncologist</source><volume>22</volume><fpage>1392</fpage><lpage>1399</lpage><year>2017</year><pub-id pub-id-type="doi">10.1634/theoncologist.2017-0078</pub-id><pub-id pub-id-type="pmid">28835513</pub-id></element-citation></ref>
<ref id="b29-ol-25-4-13740"><label>29</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Saxena</surname><given-names>P</given-names></name><name><surname>Singh</surname><given-names>PK</given-names></name><name><surname>Malik</surname><given-names>PS</given-names></name><name><surname>Singh</surname><given-names>N</given-names></name></person-group><article-title>Immunotherapy alone or in combination with chemotherapy as first-line treatment of non-small cell lung cancer</article-title><source>Curr Treat Options Oncol</source><volume>21</volume><fpage>69</fpage><year>2020</year><pub-id pub-id-type="doi">10.1007/s11864-020-00789-x</pub-id><pub-id pub-id-type="pmid">32720019</pub-id></element-citation></ref>
<ref id="b30-ol-25-4-13740"><label>30</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Sharma</surname><given-names>P</given-names></name><name><surname>Hu-Lieskovan</surname><given-names>S</given-names></name><name><surname>Wargo</surname><given-names>JA</given-names></name><name><surname>Ribas</surname><given-names>A</given-names></name></person-group><article-title>Primary, adaptive, and acquired resistance to cancer immunotherapy</article-title><source>Cell</source><volume>168</volume><fpage>707</fpage><lpage>723</lpage><year>2017</year><pub-id pub-id-type="doi">10.1016/j.cell.2017.01.017</pub-id><pub-id pub-id-type="pmid">28187290</pub-id></element-citation></ref>
<ref id="b31-ol-25-4-13740"><label>31</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Isazadeh</surname><given-names>A</given-names></name><name><surname>Hajazimian</surname><given-names>S</given-names></name><name><surname>Garshasbi</surname><given-names>H</given-names></name><name><surname>Shadman</surname><given-names>B</given-names></name><name><surname>Baghbanzadeh</surname><given-names>A</given-names></name><name><surname>Chavoshi</surname><given-names>R</given-names></name><name><surname>Taefehshokr</surname><given-names>S</given-names></name><name><surname>Farhoudi Sefidan Jadid</surname><given-names>M</given-names></name><name><surname>Hajiasgharzadeh</surname><given-names>K</given-names></name><name><surname>Baradaran</surname><given-names>B</given-names></name></person-group><article-title>Resistance mechanisms to immune checkpoints blockade by monoclonal antibody drugs in cancer immunotherapy: Focus on myeloma</article-title><source>J Cell Physiol</source><volume>236</volume><fpage>791</fpage><lpage>805</lpage><year>2021</year><pub-id pub-id-type="doi">10.1002/jcp.29905</pub-id><pub-id pub-id-type="pmid">32592235</pub-id></element-citation></ref>
<ref id="b32-ol-25-4-13740"><label>32</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Bai</surname><given-names>R</given-names></name><name><surname>Chen</surname><given-names>N</given-names></name><name><surname>Li</surname><given-names>L</given-names></name><name><surname>Du</surname><given-names>N</given-names></name><name><surname>Bai</surname><given-names>L</given-names></name><name><surname>Lv</surname><given-names>Z</given-names></name><name><surname>Tian</surname><given-names>H</given-names></name><name><surname>Cui</surname><given-names>J</given-names></name></person-group><article-title>Mechanisms of cancer resistance to immunotherapy</article-title><source>Front Oncol</source><volume>10</volume><fpage>1290</fpage><year>2020</year><pub-id pub-id-type="doi">10.3389/fonc.2020.01290</pub-id><pub-id pub-id-type="pmid">32850400</pub-id></element-citation></ref>
<ref id="b33-ol-25-4-13740"><label>33</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Li</surname><given-names>YZ</given-names></name><name><surname>Zhang</surname><given-names>HM</given-names></name></person-group><article-title>Recent advances in primary resistance mechanisms against immune checkpoint inhibitors</article-title><source>Curr Opin Oncol</source><volume>34</volume><fpage>95</fpage><lpage>106</lpage><year>2022</year><pub-id pub-id-type="doi">10.1097/CCO.0000000000000802</pub-id><pub-id pub-id-type="pmid">34669646</pub-id></element-citation></ref>
<ref id="b34-ol-25-4-13740"><label>34</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Jiao</surname><given-names>S</given-names></name><name><surname>Subudhi</surname><given-names>SK</given-names></name><name><surname>Aparicio</surname><given-names>A</given-names></name><name><surname>Ge</surname><given-names>Z</given-names></name><name><surname>Guan</surname><given-names>B</given-names></name><name><surname>Miura</surname><given-names>Y</given-names></name><name><surname>Sharma</surname><given-names>P</given-names></name></person-group><article-title>Differences in tumor microenvironment dictate T helper lineage polarization and response to immune checkpoint therapy</article-title><source>Cell</source><volume>179</volume><fpage>1177</fpage><lpage>1190</lpage><lpage>e13</lpage><year>2019</year><pub-id pub-id-type="doi">10.1016/j.cell.2019.10.029</pub-id><pub-id pub-id-type="pmid">31730856</pub-id></element-citation></ref>
<ref id="b35-ol-25-4-13740"><label>35</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Qin</surname><given-names>BD</given-names></name><name><surname>Jiao</surname><given-names>XD</given-names></name><name><surname>Liu</surname><given-names>J</given-names></name><name><surname>Liu</surname><given-names>K</given-names></name><name><surname>He</surname><given-names>X</given-names></name><name><surname>Wu</surname><given-names>Y</given-names></name><name><surname>Ling</surname><given-names>Y</given-names></name><name><surname>Duan</surname><given-names>XP</given-names></name><name><surname>Qin</surname><given-names>WX</given-names></name><name><surname>Wang</surname><given-names>Z</given-names></name><name><surname>Zang</surname><given-names>YS</given-names></name></person-group><article-title>The effect of liver metastasis on efficacy of immunotherapy plus chemotherapy in advanced lung cancer</article-title><source>Crit Rev Oncol Hematol</source><volume>147</volume><fpage>102893</fpage><year>2020</year><pub-id pub-id-type="doi">10.1016/j.critrevonc.2020.102893</pub-id><pub-id pub-id-type="pmid">32065969</pub-id></element-citation></ref>
<ref id="b36-ol-25-4-13740"><label>36</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>McKean</surname><given-names>WB</given-names></name><name><surname>Moser</surname><given-names>JC</given-names></name><name><surname>Rimm</surname><given-names>D</given-names></name><name><surname>Hu-Lieskovan</surname><given-names>S</given-names></name></person-group><article-title>Biomarkers in precision cancer immunotherapy: Promise and challenges</article-title><source>Am Soc Clin Oncol Educ Book</source><volume>40</volume><fpage>e275</fpage><lpage>e291</lpage><year>2020</year><pub-id pub-id-type="doi">10.1200/EDBK_280571</pub-id><pub-id pub-id-type="pmid">32453632</pub-id></element-citation></ref>
<ref id="b37-ol-25-4-13740"><label>37</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Ramaswamy</surname><given-names>G</given-names></name><name><surname>Rao</surname><given-names>VR</given-names></name><name><surname>Krishnamoorthy</surname><given-names>L</given-names></name><name><surname>Ramesh</surname><given-names>G</given-names></name><name><surname>Gomathy</surname><given-names>R</given-names></name><name><surname>Renukadevi</surname><given-names>D</given-names></name></person-group><article-title>Serum levels of bone alkaline phosphatase in breast and prostate cancers with bone metastasis</article-title><source>Indian J Clin Biochem</source><volume>15</volume><fpage>110</fpage><lpage>113</lpage><year>2000</year><pub-id pub-id-type="doi">10.1007/BF02883737</pub-id><pub-id pub-id-type="pmid">23105250</pub-id></element-citation></ref>
<ref id="b38-ol-25-4-13740"><label>38</label><element-citation publication-type="journal"><person-group person-group-type="author"><name><surname>Hu</surname><given-names>J</given-names></name><name><surname>Yang</surname><given-names>S</given-names></name><name><surname>Wang</surname><given-names>J</given-names></name><name><surname>Zhang</surname><given-names>Q</given-names></name><name><surname>Zhao</surname><given-names>L</given-names></name><name><surname>Zhang</surname><given-names>D</given-names></name><name><surname>Yu</surname><given-names>D</given-names></name><name><surname>Jin</surname><given-names>M</given-names></name><name><surname>Ma</surname><given-names>H</given-names></name><name><surname>Liu</surname><given-names>H</given-names></name><etal/></person-group><article-title>Blood alkaline phosphatase predicts prognosis of patients with advanced HER2-negative gastric cancer receiving immunotherapy</article-title><source>Ann Transl Med</source><volume>9</volume><fpage>1316</fpage><year>2021</year><pub-id pub-id-type="doi">10.21037/atm-21-3376</pub-id><pub-id pub-id-type="pmid">34532453</pub-id></element-citation></ref>
</ref-list>
</back>
<floats-group>
<fig id="f1-ol-25-4-13740" position="float">
<label>Figure 1.</label>
<caption><p>Bone and liver metastasis restrain efficacy of ICIs treatment. (A) Response to ICIs treatment of patients with NSCLC with or without bone metastasis. (B) mPFS of patients with NSCLC with or without bone metastasis after ICIs treatment. (C) Response to ICIs treatment of patients with NSCLC with or without liver metastasis. (D) mPFS of patients with NSCLC with or without liver metastasis after ICIs treatment. (E) ALP levels in patients with NSCLC with or without bone metastasis and liver metastasis. &#x002A;P&#x003C;0.05, &#x002A;&#x002A;P&#x003C;0.01. ALP, alkaline phosphatase; ICIs, immune checkpoint inhibitors; iCPD, progressive disease; iPR, partial response; iSD, stable disease; NSCLC, non-small cell lung cancer; mPFS, median progression-free survival.</p></caption>
<graphic xlink:href="ol-25-04-13740-g00.tif"/>
</fig>
<fig id="f2-ol-25-4-13740" position="float">
<label>Figure 2.</label>
<caption><p>ALP levels predict efficacy of ICIs treatment in patients with NSCLC. (A) ALP levels in responders and non-responders to ICIs treatment. (B) Response to ICIs treatment of patients with NSCLC with or without high ALP levels. (C) Progression-free survival of patients with NSCLC with or without high ALP levels after ICIs treatment. &#x002A;P&#x003C;0.05, &#x002A;&#x002A;P&#x003C;0.01. ALP, alkaline phosphatase; ICIs, immune checkpoint inhibitors; iCPD, progressive disease; iSD, stable disease; NSCLC, non-small cell lung cancer; iPR, partial response.</p></caption>
<graphic xlink:href="ol-25-04-13740-g01.tif"/>
</fig>
<fig id="f3-ol-25-4-13740" position="float">
<label>Figure 3.</label>
<caption><p>Forest plot of univariate analyses of different parameters for progression-free survival. AD, adenocarcinoma; ALP, alkaline phosphatase; HR, hazard ratio; SC, squamous cancer.</p></caption>
<graphic xlink:href="ol-25-04-13740-g02.tif"/>
</fig>
<table-wrap id="tI-ol-25-4-13740" position="float">
<label>Table I.</label>
<caption><p>Baseline characteristics of 143 patients with lung cancer.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th align="left" valign="bottom">Characteristics</th>
<th align="center" valign="bottom">No. (&#x0025;)</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="top">Age, years</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x2265;60</td>
<td align="center" valign="top">61 (42.7)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x003C;60</td>
<td align="center" valign="top">82 (57.3)</td>
</tr>
<tr>
<td align="left" valign="top">Sex</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Male</td>
<td align="center" valign="top">113 (79.0)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Female</td>
<td align="center" valign="top">30 (21.0)</td>
</tr>
<tr>
<td align="left" valign="top">Histology type</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;SC</td>
<td align="center" valign="top">74 (51.7)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;AD</td>
<td align="center" valign="top">69 (48.3)</td>
</tr>
<tr>
<td align="left" valign="top">TNM stage</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;III</td>
<td align="center" valign="top">18 (12.6)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;IV</td>
<td align="center" valign="top">125 (87.4)</td>
</tr>
<tr>
<td align="left" valign="top">Metastatic sites</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Bone only</td>
<td align="center" valign="top">45 (31.4)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Liver only</td>
<td align="center" valign="top">10 (7.0)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Both bone and liver</td>
<td align="center" valign="top">17 (11.9)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Neither bone or liver</td>
<td align="center" valign="top">71 (49.7)</td>
</tr>
<tr>
<td align="left" valign="top">Treatment lines</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;1st</td>
<td align="center" valign="top">85 (59.4)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x2265;2nd</td>
<td align="center" valign="top">58 (40.6)</td>
</tr>
<tr>
<td align="left" valign="top">Combined therapy</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Yes</td>
<td align="center" valign="top">65 (45.5)</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;No</td>
<td align="center" valign="top">78 (54.5)</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="tfn1-ol-25-4-13740"><p>AD, adenocarcinoma; SC, squamous cancer.</p></fn>
</table-wrap-foot>
</table-wrap>
<table-wrap id="tII-ol-25-4-13740" position="float">
<label>Table II.</label>
<caption><p>Association between clinical variables and serum ALP levels.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th/>
<th align="center" valign="bottom" colspan="2">Pretreatment ALP levels</th>
<th/>
</tr>
<tr>
<th/>
<th align="center" valign="bottom" colspan="2"><hr/></th>
<th/>
</tr>
<tr>
<th align="left" valign="bottom">Characteristics</th>
<th align="center" valign="bottom">&#x2265;110 U/l, n</th>
<th align="center" valign="bottom">&#x003C;110 U/l, n</th>
<th align="center" valign="bottom">P-value</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="top">Age, years</td>
<td/>
<td/>
<td align="center" valign="top">0.809</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x2265;60</td>
<td align="center" valign="top">16</td>
<td align="center" valign="top">45</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x003C;60</td>
<td align="center" valign="top">23</td>
<td align="center" valign="top">59</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Sex</td>
<td/>
<td/>
<td align="center" valign="top">0.402</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Male</td>
<td align="center" valign="top">29</td>
<td align="center" valign="top">84</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Female</td>
<td align="center" valign="top">10</td>
<td align="center" valign="top">20</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Histology type</td>
<td/>
<td/>
<td align="center" valign="top">0.931</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;SC</td>
<td align="center" valign="top">21</td>
<td align="center" valign="top">53</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;AD</td>
<td align="center" valign="top">18</td>
<td align="center" valign="top">51</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Stage</td>
<td/>
<td/>
<td align="center" valign="top">0.100</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;III</td>
<td align="center" valign="top">2</td>
<td align="center" valign="top">16</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;IV</td>
<td align="center" valign="top">37</td>
<td align="center" valign="top">88</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Bone metastasis</td>
<td/>
<td/>
<td align="center" valign="top">&#x003C;0.001</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Yes</td>
<td align="center" valign="top">34</td>
<td align="center" valign="top">28</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;No</td>
<td align="center" valign="top">5</td>
<td align="center" valign="top">76</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Liver metastasis</td>
<td/>
<td/>
<td align="center" valign="top">0.036</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Yes</td>
<td align="center" valign="top">10</td>
<td align="center" valign="top">17</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;No</td>
<td align="center" valign="top">29</td>
<td align="center" valign="top">87</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Bone and liver metastasis</td>
<td/>
<td/>
<td align="center" valign="top">&#x003C;0.001</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Both</td>
<td align="center" valign="top">10</td>
<td align="center" valign="top">7</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Neither</td>
<td align="center" valign="top">4</td>
<td align="center" valign="top">67</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Treatment lines</td>
<td/>
<td/>
<td align="center" valign="top">0.945</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;1st</td>
<td align="center" valign="top">23</td>
<td align="center" valign="top">62</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;&#x2265;2nd</td>
<td align="center" valign="top">16</td>
<td align="center" valign="top">42</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">Combined therapy</td>
<td/>
<td/>
<td align="center" valign="top">0.304</td>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;Yes</td>
<td align="center" valign="top">15</td>
<td align="center" valign="top">50</td>
<td/>
</tr>
<tr>
<td align="left" valign="top">&#x00A0;&#x00A0;No</td>
<td align="center" valign="top">24</td>
<td align="center" valign="top">54</td>
<td/>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="tfn2-ol-25-4-13740"><p>AD, adenocarcinoma; ALP, alkaline phosphatase; SC, squamous cancer.</p></fn>
</table-wrap-foot>
</table-wrap>
<table-wrap id="tIII-ol-25-4-13740" position="float">
<label>Table III.</label>
<caption><p>Univariate and multivariate analyses of different parameters for progression-free survival.</p></caption>
<table frame="hsides" rules="groups">
<thead>
<tr>
<th/>
<th align="center" valign="bottom" colspan="3">Univariate</th>
<th align="center" valign="bottom" colspan="3">Multivariate</th>
</tr>
<tr>
<th/>
<th align="center" valign="bottom" colspan="3"><hr/></th>
<th align="center" valign="bottom" colspan="3"><hr/></th>
</tr>
<tr>
<th align="left" valign="bottom">Variables</th>
<th align="center" valign="bottom">HR</th>
<th align="center" valign="bottom">95&#x0025; CI</th>
<th align="center" valign="bottom">P-value</th>
<th align="center" valign="bottom">HR</th>
<th align="center" valign="bottom">95&#x0025; CI</th>
<th align="center" valign="bottom">P-value</th>
</tr>
</thead>
<tbody>
<tr>
<td align="left" valign="top">Sex (male vs. female)</td>
<td align="center" valign="top">1.274</td>
<td align="center" valign="top">0.731-2.219</td>
<td align="center" valign="top">0.417</td>
<td/>
<td/>
<td/>
</tr>
<tr>
<td align="left" valign="top">Age (&#x2265;60 vs. &#x003C;60 years)</td>
<td align="center" valign="top">1.028</td>
<td align="center" valign="top">0.653-1.617</td>
<td align="center" valign="top">0.903</td>
<td/>
<td/>
<td/>
</tr>
<tr>
<td align="left" valign="top">Histology (SC vs. AD)</td>
<td align="center" valign="top">1.402</td>
<td align="center" valign="top">0.889-2.209</td>
<td align="center" valign="top">0.134</td>
<td align="center" valign="top">0.511</td>
<td align="center" valign="top">0.302-0.863</td>
<td align="center" valign="top">0.012</td>
</tr>
<tr>
<td align="left" valign="top">Stage (III vs. IV)</td>
<td align="center" valign="top">0.343</td>
<td align="center" valign="top">0.195-0.603</td>
<td align="center" valign="top">0.006</td>
<td align="center" valign="top">3.104</td>
<td align="center" valign="top">1.213-7.944</td>
<td align="center" valign="top">0.018</td>
</tr>
<tr>
<td align="left" valign="top">Bone metastasis (no vs. yes)</td>
<td align="center" valign="top">0.563</td>
<td align="center" valign="top">0.349-0.907</td>
<td align="center" valign="top">0.010</td>
<td align="center" valign="top">1.174</td>
<td align="center" valign="top">0.856-2.641</td>
<td align="center" valign="top">0.103</td>
</tr>
<tr>
<td align="left" valign="top">Liver metastasis (no vs. yes)</td>
<td align="center" valign="top">0.658</td>
<td align="center" valign="top">0.356-1.217</td>
<td align="center" valign="top">0.119</td>
<td/>
<td/>
<td/>
</tr>
<tr>
<td align="left" valign="top">Treatment lines (1st vs. &#x2265;2nd)</td>
<td align="center" valign="top">0.898</td>
<td align="center" valign="top">0.548-1.472</td>
<td align="center" valign="top">0.662</td>
<td/>
<td/>
<td/>
</tr>
<tr>
<td align="left" valign="top">Combined therapy (yes vs. no)</td>
<td align="center" valign="top">1.453</td>
<td align="center" valign="top">0.804-2.262</td>
<td align="center" valign="top">0.199</td>
<td/>
<td/>
<td/>
</tr>
<tr>
<td align="left" valign="top">ALP (&#x003C;110 vs. &#x2265;110 U/l)</td>
<td align="center" valign="top">1.838</td>
<td align="center" valign="top">1.609-3.191</td>
<td align="center" valign="top">0.009</td>
<td align="center" valign="top">1.856</td>
<td align="center" valign="top">1.030-3.343</td>
<td align="center" valign="top">0.040</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="tfn3-ol-25-4-13740"><p>AD, adenocarcinoma; ALP, alkaline phosphatase; HR, hazard ratio; SC, squamous cancer.</p></fn>
</table-wrap-foot>
</table-wrap>
</floats-group>
</article>
