The study evaluated the safety and efficacy of neoadjuvant nivolumab plus ipilimumab in patients with locally advanced mismatch repair-deficient (dMMR) colon cancer. The primary endpoints were timely surgery and 3-year disease-free survival, while secondary endpoints included pathological response and genomic analyses. Of the 115 enrolled patients, 113 underwent timely surgery, with only 2 patients experiencing delays due to immune-related adverse events. A pathological response was observed in 109 patients (98%), including 105 with a major pathological response (≤10% residual viable tumor) and 75 with a pathological complete response (0% residual viable tumor). No patients experienced disease recurrence at a median follow-up of 26 months. The study concluded that neoadjuvant nivolumab plus ipilimumab had an acceptable safety profile and led to a high proportion of pathological responses in patients with locally advanced dMMR colon cancer.The study evaluated the safety and efficacy of neoadjuvant nivolumab plus ipilimumab in patients with locally advanced mismatch repair-deficient (dMMR) colon cancer. The primary endpoints were timely surgery and 3-year disease-free survival, while secondary endpoints included pathological response and genomic analyses. Of the 115 enrolled patients, 113 underwent timely surgery, with only 2 patients experiencing delays due to immune-related adverse events. A pathological response was observed in 109 patients (98%), including 105 with a major pathological response (≤10% residual viable tumor) and 75 with a pathological complete response (0% residual viable tumor). No patients experienced disease recurrence at a median follow-up of 26 months. The study concluded that neoadjuvant nivolumab plus ipilimumab had an acceptable safety profile and led to a high proportion of pathological responses in patients with locally advanced dMMR colon cancer.