Safety of concurrent immune checkpoint inhibitor therapy during postoperative radiotherapy for triple‑negative breast cancer: A preliminary retrospective analysis

Immune checkpoint inhibitors (ICIs) have recently been approved as part of a neoadjuvant therapy plan for triple‑negative breast cancer (TNBC). Consequently, the concurrent use of radiotherapy (RT) and ICIs is becoming increasingly common in clinical practice. Combining RT with ICIs may increase the risk of radiation pneumonitis. However, evidence remains limited regarding whether concurrent ICIs administered during postoperative RT increase the risk of radiation pneumonitis in patients with TNBC. The aim of the present preliminary, single‑centre, retrospective, hypothesis‑generating study was to evaluate the incidence of radiation pneumonitis in patients with TNBC treated with concurrent ICIs and RT. Patients with TNBC, who were treated at Hubei Cancer Hospital (Wuhan, China) between 2022 and 2024, were retrospectively enrolled. The inclusion criteria were receipt of neoadjuvant chemotherapy with or without ICIs, followed by postoperative adjuvant RT. Patients were divided into two groups: Postoperative RT with concurrent ICIs (ICIs‑RT) and postoperative RT alone (RT‑alone group). Baseline clinical characteristics, treatment responses, RT parameters and follow‑up CT scans for the assessment of radiation pneumonitis were documented. The χ² test and Student's t‑test were used for the statistical analyses. A total of 132 patients with TNBC were enrolled. The pathological complete response rate following neoadjuvant therapy was significantly higher in patients who subsequently received postoperative ICIs‑RT than in those who received RT alone (46.7 vs. 22.5%; P=0.01). Of the 132 patients, 30 received ICIs‑RT and 102 received RT alone. In the ICIs‑RT group, 5 patients received pembrolizumab, 22 received tislelizumab, 1 received camrelizumab and 2 received toripalimab. Follow‑up assessments, including contrast‑enhanced CT scans, were performed every 3 months for 1 year. The incidence of grade 1 radiation pneumonitis was 63.3% (19/30) in the ICIs‑RT group and 46.1% (47/102) in the RT‑alone group, with no statistically significant difference between the groups. No grade 2 or higher radiation pneumonitis occurred in either group. Hypothyroidism was observed in 33.3% (10/30) of patients in the ICIs‑RT group, which was significantly higher than the 11.8% (12/102) observed in the RT‑alone group (P=0.01). The incidence of grade 1 radiation dermatitis was 10.0% (3/30) in the ICIs‑RT group and 9.8% (10/102) in the RT‑alone group, whereas the incidence of grade 2 radiation dermatitis was 90.0% (27/30) and 90.2% (92/102), respectively, with no significant difference between the groups. In patients with TNBC previously treated with neoadjuvant ICIs, the addition of concurrent ICIs to postoperative RT did not significantly increase the incidence of radiation dermatitis. Regarding radiation pneumonitis, no statistically significant increase was observed; however, a clinically meaningful trend toward a higher incidence of grade 1 radiation pneumonitis cannot be excluded. An increased risk of hypothyroidism was observed, likely attributable to immune‑related adverse effects of ICIs. These preliminary findings require validation in larger prospective trials.