A phase II evaluation of pembrolizumab in recurrent microsatellite instability-high (MSI-H) endometrial cancer patients with Lynch-like versus MLH-1 methylated characteristics (NCT02899793).

5523 Background: Microsatellite instability (MSI-H) is a biomarker for response to immune-checkpoint inhibitors (ICIs); however, these neoplasms are heterogenous including Lynch (germline), Lynch-like (somatic) and sporadic ( MLH1-methylated) tumors. Whether mechanisms underlying MSI alter responses to ICIs is unclear. We report data from a phase II pilot study (NCT02899793) of pembrolizumab in recurrent MSI-H endometrial cancer (EC) patients...