1 patient had a mutation in MSH6, 1 patient had 2 mutations in MSH2, another had loss of MLH1/PMS2 on IHC, and the last patient had loss of MSH2/MSH6 on IHC...Median follow-up is 25.5 months [range: 9-42] and 1 pt continues on nivo treatment. Pts were treated with 1-4 infusions of ipi and 2-24 months of nivolumab. All patients achieved a complete clinical/pathologic response and remain without evidence of disease recurrence...The use of ipi/nivo in this cohort of pts resulted in complete pathogenic responses for all that remain durable over an extended period of time...