Pembrolizumab & DostarlimabAssessing Survival Outcomes With Checkpoint Inhibition ExteNded vs Discontinued in Endometrial Cancer

This is a pragmatic, non-inferiority randomized hybrid decentralized clinical trial. The goal of this study is to determine if one year of maintenance immunotherapy (anti-PD1 agent therapy; pembrolizumab or dostarlimab) is non-inferior to two years of maintenance therapy for patients with advanced/metastatic or recurrent endometrial cancer who have completed the standard course of cytotoxic chemotherapy plus anti-PD1 therapy (chemoimmunotherapy). Our hypothesis is that one year of maintenance therapy will be comparable, or statistically non-inferior, to two years of therapy. This question has clinical importance as there is not a clear optimal duration for maintenance immunotherapy in this setting, and checkpoint inhibitors are associated with their own unique toxicity profile (immune-related adverse events) and incremental costs to patients and the healthcare system at large. Patients who respond favorably to primary therapy and choose to enroll will be randomized (1:1) after completion of chemoimmunotherapy to one-year of maintenance anti-PD1 therapy (1-year arm) or to two-years of maintenance anti-PD1 therapy (2-year arm). The primary endpoint is progression-free survival (PFS) determined over the course of at least 3 years from randomization of patient follow up. Secondary endpoints are overall survival (OS) and incidence of immune-related adverse events (irAE). Finally, exploratory objectives include measuring differences in gut and vaginal microbial profiles and innate immune system (IIS) tumor profiles and correlation with clinical outcomes (PFS, OS).