Radiologic Progression of Disease during Neoadjuvant Dostarlimab in Mismatch Repair-Deficient Lynch-Associated Locally Advanced Rectal Cancer Resulting in Pathologic Complete Response: A Case Report

Background

Neoadjuvant PD-1 blockade has demonstrated unprecedented activity in mismatch repair-deficient (dMMR) locally advanced rectal cancer (LARC), with high rates of clinical complete response and increasing adoption of organ-preservation strategies. However, response assessment during immunotherapy remains challenging as immune-mediated tumor regression may generate radiologic patterns that mimic persistent or progressive disease.