We report on a post-hoc analysis of ORR with loss of MMR dimers and mutation status of MMR genes in patients with dMMR endometrial cancer (EC) treated with dostarlimab....Cohort A1 included 143 patients; MMR gene mutation data was available for 101 (Table). Cohort A1 ORR was 45.5%. 66% of patients had loss of MLH1/PMS2; ORR was 48.9%. 11.2% of patients had loss of MSH2/MSH6; ORR was 56.2%. ORR was 41.7% for MLH1 loss with MMR gene mutation and 39.4% for MLH1 loss without MMR gene mutation....Patients with dMMR advanced/recurrent EC benefitted from dostarlimab...