A retrospective cohort study of neoadjuvant chemoradiotherapy combined with immune checkpoint inhibitors in locally advanced rectal cancer.

Introduction: This study aimed to investigate the safety and efficacy of neoadjuvant chemoradiotherapy combined with immune checkpoint inhibitors (ICIs) in patients with locally advanced rectal cancer (LARC). Patients diagnosed with LARC and treated with programmed cell death protein-1 (PD-1) inhibitors were recruited.

Methods: Four different treatment strategies were employed in this study: plan A [long-course radiotherapy + PD-1 inhibitor/capecitabine + PD-1 inhibitor/XELOX+ total mesorectal excision (TME)], plan B (long-course radiotherapy + capecitabine + PD-1 inhibitor/XELOX + TME), plan C (short-course radiotherapy + PD-1 inhibitor/XELOX + TME), and plan D (PD-1 inhibitor/XELOX + short-course radiotherapy + TME). The basic information about patients, pathological indicators, adverse events, and efficacy indexes of treatment plans were analyzed.

Results: 96.8 % of patients were mismatch repair proficient (pMMR) and only 2 patients belonged to mismatch repair deficient (dMMR). The 2 patients with dMMR showed a pathological complete response (pCR) rate of 100 %, while the pCR rate of pMMR patients was 43.3 %. The overall tumor descending rate reached 79 %, and the anus-retained rate was 88.7 % in all LARC patients. Plan A exhibited the highest pCR rate of 60 %, and plan C had the highest tumor descending rate and anal preservation rate. Radiation enteritis was the most common adverse event in LARC patients after neoadjuvant therapy, and its incidence was the highest in Plan A.

Conclusion: Neoadjuvant chemoradiotherapy combined with ICIs demonstrated favorable efficacy and safety in treating LARC patients.