A multicentre phase II study (NICHE-2; NCT03026140) conducted by the Netherlands Cancer Institute has investigated the safety and efficacy of neoadjuvant immunotherapy in patients with locally advanced, mismatch repair-deficient colon cancer. Patients (n = 115 enrolled) were treated with neoadjuvant nivolumab (PD1 inhibitor) plus ipilimumab (CTLA4 inhibitor). After treatment, 113 patients (98%; 97.5% CI 93–100) underwent timely surgery. Of 111 patients included in the efficacy analysis, 109 patients exhibited a pathological response (98%; 95% CI 94–100). No patients discontinued treatment due to adverse events, and no patients had disease recurrence after a 26-month median follow-up.