RecruitingPhase 2Drug trialImmunotherapy in Patients With Early dMMR Rectal CancerThe purpose of this investigator-initiated, multicenter phase II trial is to evaluate the efficacy and tolerability of nivolumab and ipilimumab in patients with stage 1-3 MSI/dMMR rectal cancer. The primary objective is: Number of patients with complete clinical response after one or two cycles of immunotherapy. Patients will be treated with 1 or 2 cycles of combination immunotherapy: Cycle 1: Nivolumab 3 mg/kg days 1 and 15 \& ipilimumab 1 mg/kg day 1 Cycle 2: Nivolumab 3 mg/kg days 50 and 65 \& ipilimumab 1 mg/kg day 50