Abstract
BACKGROUND: Endoscopy allows for the direct observation of primary tumor characteristics and responses after neoadjuvant treatment. However, reports on endoscopic evaluation following neoadjuvant immunotherapy remain limited. AIM: To examine the predictive value of endoscopic findings of primary tumors for responses to neoadjuvant immunotherapy. METHODS: This retrospective study, conducted at a tertiary center in China, evaluated 74 patients with colorectal cancer, including 17 with deficient mismatch repair (dMMR) and 15 with proficient mismatch repair (pMMR) tumors. Patients underwent neoadjuvant immunotherapy followed by surgery. Endoscopic findings before and after neoadjuvant immunotherapy were reviewed and compared with the pathology of the resected specimens. RESULTS: In the pMMR group (n = 57 evaluable patients), endoscopy identified 11/17 patients who achieved a complete response (CR), while misidentifying 1/40 patients with residual disease as CR (64.7% vs 2.5%, P < 0.01). Conversely, 22/40 patients with residual disease were accurately identified as achieving a partial response (PR), with 1/17 patients who achieved CR misclassified as PR (55.0% vs 5.9%, P < 0.01). The sensitivity, specificity, and accuracy of endoscopic diagnosis for pathological CR were 64.7%, 97.5%, and 87.7%, respectively. In the dMMR cohort, endoscopy classified 9/17 patients as CR and 2 of the remaining patients with residual tumors as PR (64.3% vs 66.7%, P = 0.73). The method demonstrated 100% sensitivity and 82.4% accuracy in diagnosing pathological CR. CONCLUSION: Endoscopic evidence of CR or PR was well correlated with postoperative pathological outcomes in the pMMR cohort. Despite endoscopic indications of tumor residue, a complete pathological response post-surgery was possible in the dMMR cohort.