NICHE-3 study, approved by NedMec, enrolled adults with dMMR resectable colon adenocarcinoma. Patients received nivolumab and relatlimab, followed by surgery. Primary endpoint was pathologic response (≤50% RVT), with secondary endpoints including safety and survival. Study used a Simon’s two-stage design, aiming for a response rate of 85%. Pathologic response was assessed by central histopathologic review. Safety and efficacy populations were defined, with binary endpoints reported as proportions. MMR status was assessed via immunohistochemistry.