No more surgery by default in dMMR/MSI-H colon cancer? From mandatory colectomy to response-adapted surgery.

Abstract

Neoadjuvant immune checkpoint blockade has transformed localized mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) colon cancer, producing unprecedented rates of major and complete pathological response. These results raise a question that until recently would have seemed premature: should colectomy remain mandatory in every complete responder? We argue that the next step is not routine omission of surgery, but prospective testing of response-adapted surgery. The central obstacle is no longer treatment efficacy, but reliable identification of a true complete response before resection. Unlike rectal cancer, colon cancer lacks a clinical complete response consensus framework, while residual nodal disease remains difficult to exclude. Endoscopy, imaging and circulating tumour DNA provide complementary information, but none is yet sufficient alone. Emerging trials are now directly testing non-operative strategies. Surgery should therefore remain standard outside clinical trials, while becoming a conditional intervention within carefully designed response-adapted studies.