Patient with synchronous Disparate-MMR Pelvic Primaries (Stage IIIC dMMR Endometrial & T3/T4 pMMR low-lying Rectal) receiving chemoradiation to avoid an APR. The patient received 3 cycles of carbo/taxol/pembro for endometrial cancer prior to the diagnosis of rectal cancer. 1. Given that we are pursuing a non-operative approach for the pMMR rectal cancer to avoid a permanent colostomy, how would you approach local control for the Stage IIIC endometrial cancer after pelvic radiation? 2. Following NRG-GI002 data and GY018/KEYNOTE-868 in a discordant MMR dual-primary cancer patient, would you continue maintenance pembrolizumab post-radiation?