Study of Pembrolizumab (MK-3475) in Combination With Adjuvant Chemotherapy With or Without Radiotherapy in Participants With Newly Diagnosed Endometrial Cancer After Surgery With Curative Intent (MK-3475-B21 / KEYNOTE-B21 / ENGOT-en11 / GOG-3053)

The purpose of this study is to compare pembrolizumab + adjuvant chemotherapy with placebo + adjuvant chemotherapy, with or without radiotherapy, with respect to disease-free survival (DFS) as assessed radiographically by the investigator or by histopathologic confirmation of suspected disease recurrence, and with respect to overall survival (OS). The primary hypotheses are that pembrolizumab + adjuvant chemotherapy is superior to placebo + adjuvant chemotherapy, with or without radiotherapy, with respect to DFS as assessed radiographically by the investigator or by histopathologic confirmation of suspected disease recurrence, and with respect to OS.