Between January, 2000 and December, 2011, 616 patients with primary CRC who underwent surgical treatment at the Department of Gastrointestinal Surgery, Mie University Hospital (Tsu, Mie, Japan) were enrolled in this study. Among these prospectively enrolled patients, 468 underwent open colorectal surgery and 148 underwent laparoscopic surgery. Data for all the patients, including demographics, comorbidities, operative results, complications, mortality and outcomes at follow-up, were entered into a prospective database. The comorbidity status was objectively evaluated using the American Society of Anesthesiologists (ASA) score and the Charlson Comorbidity Index (CCI) (15), which is a partially modified score, not including cancer or age (16). The body mass index (BMI) was recorded to assess the difficulty of laparoscopic surgery. All the patients underwent bowel preparation on the day prior to surgery by intestinal washout with an isosmotic solution. All the patients received antibiotic prophylaxis with cefmetazole during the introduction of anesthesia and again twice daily for 1 or 2 consecutive days after surgery.

All the laparoscopic surgeries were performed or supervised by the same team of colorectal surgeons. The exclusion criteria for laparoscopic surgery incuded T4 or bulky tumor, extended peritoneal dissemination, preoperative chemotherapy and/or radiotherapy, intestinal obstruction, palliative surgery and emergency surgery. In our study, we also compared the differences between patients undergoing laparoscopic surgery and 259 matched patients with stage I-III CRC who underwent open surgery, using the same exclusion criteria.

Mortality was defined as death occurring during the hospital stay or within 30 days after surgery. An operative complication was defined as an event that prolonged the hospital stay or led to an additional procedure.

Informed consent was obtained from all the patients who underwent surgical treatment at our institution. Approval from the Institutional Review Board was obtained for the use of patient data in the present study.

Conventional laparoscopic surgery was performed as a laparoscopic-assisted procedure, with removal of the resected specimen via a 4-cm horizontal supraumbilical minilaparotomy. Laparoscopic surgery was performed using a 5-trocar technique, with one 12-mm trocar inserted via a paraumbilical incision and three 5-mm trocars and one 12-mm trocar inserted in the right and left lower abdomen. Following removal of the resected specimen and creation of the stapled anastomosis, we closed the minilaparotomy and reintroduced pneumoperitoneum. We also used single-port laparoscopic surgery for certain patients with right-sided colon cancer.

The patients were categorized into two groups based on age, namely an elderly group, aged >75 years and a non-elderly group, aged <75 years. The cut-off of 75 years was selected as ~40% of the CRC cases are patients aged >75 years and the incidence of CRC increases with advancing age (1–4).

JMP version 7 software (SAS Institute Inc., Cary, NC, USA) was used to perform the statistical analyses. Data are presented as mean ± standard deviation. Contingency tables were analyzed using the Fisher's exact test or the χ² test with Yates' correction. The correlations between continuous and categorical variables were evaluated using the Mann-Whitney U test. Kaplan-Meier survival curves were constructed and the differences were analyzed using the log-rank test. Each significant predictor identified was assessed by multivariate analysis using a logistic regression model. P<0.05 was considered to indicate a statistically significant difference.

A total of 148 consecutive patients [74 men and 74 women; mean age, 68 years (range, 37–89 years)] who underwent laparoscopic surgery for CRC between January, 2000 and December, 2011 were included in this analysis. Of the 148 patients, 48 were classified as elderly (mean age ± SD, 78.6±3.1 years; range, 75–89 years) and 100 as non-elderly (62.9±7.8 years; range, 37–74 years). The background characteristics of the 148 patients by age group are summarized in Table I. There were no significant differences in gender, BMI, tumor characteristics and type of surgical procedure between the elderly and non-elderly groups. There were significant correlations between age and ASA score (P=0.0163). Of the 148 patients, 34 (23.0%) had cardiovascular disease, which was the most common comorbidity. The two groups exhibited similar rates of comorbidities and the CCI did not significantly differ between the elderly (0.54±0.42) and non-elderly (0.70±0.90) groups. However, the elderly group exhibited a higher incidence of cardiovascular disease (35.4 vs. 17.0%, respectively; P=0.0127) and pulmonary disease (18.8 vs. 8.0%, respectively; P=0.0628) when compared to the non-elderly group.

The short-term outcomes for all the patients are summarized in Table II. There were no significant differences between the two groups regarding surgical outcomes, including operating time, intraoperative blood loss, lymph node harvest, complications and duration of hospital stay. Postoperative major and minor complications occurred in 24 (16.2%) of the 148 patients. A comparison between patients with and those without postoperative complications, performed to determine the potential effects of patient-, tumor- and treatment-related factors on complications, identified significant correlations with ASA 2–3 (P=0.0204) and pulmonary disease (P=0.0055). The multivariate analysis revealed that pulmonary disease, but not age, was an independent factor affecting postoperative complications (odds ratio = 3.21, 95% confidence interval: 1.02–10.14; P=0.0470) (Table III). In our study, pulmonary comorbidities included chronic obstructive pulmonary disease, pneumonia, bronchiolitis, bronchiectasis, bronchial asthma and history of major surgery for lung cancer. A total of 17 patients had preoperative pulmonary disease, including 9 elderly (18.8%) and 8 non-elderly (8%) patients (Table I). Of these patients, 7 (41.2%) had postoperative complications covering a wide range of conditions, including 1 case of pneumonia, 1 case of respiratory disorder, 2 surgical site infections, 1 case of persistent bleeding, 1 urinary tract infection and 1 case of paralysis. There was 1 reported case of mortality in our study: An 85-year-old man with both pulmonary and cardiovascular disease succumbed to pneumonia 2 weeks following surgery.

Postoperative complications occurred in 81 (31.3%) of the 259 matched patients who underwent open colorectal surgery during the same period. The incidence of complications was significantly higher with open surgery compared with laparoscopic surgery (31.3 vs. 16.2%, respectively; P=0.0008). Of the 259 patients, 128 (49.8%) exhibited comorbidities, including pulmonary comorbidity in 15 patients who underwent open surgery. Of note, the pulmonary comorbidity did not affect the postoperative complications in the open surgery group, unlike in the laparoscopic surgery group. The rates of postoperative complications in patients with pulmonary comorbidities were similar between the laparoscopic and open surgery groups (41.2 vs. 46.7%, respectively; P=0.7547) (data not shown).

After a median follow-up of 51.2 months, we assessed overall survival using Kaplan-Meier survival analysis. There were no significant differences in recurrence rates between the elderly and non-elderly groups (4.2 vs. 5.0%, respectively; P=0.7637). The 5-year overall survival also did not differ between the elderly and non-elderly groups (97.9 vs. 96.7%, respectively; P=0.4955) (data not shown). There was no correlation of preoperative comorbidities or postoperative complications with oncological outcome in our study.