Testing the Addition of the Immunotherapy Drug Pembrolizumab to the Usual Chemotherapy Treatment (Paclitaxel and Carboplatin) in Stage III-IV or Recurrent Endometrial Cancer

This phase III trial studies how well the combination of pembrolizumab, paclitaxel and carboplatin works compared with paclitaxel and carboplatin alone in treating patients with endometrial cancer that is stage III or IV, or has come back after a period of improvement (recurrent). Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Paclitaxel and carboplatin are chemotherapy drugs used as part of the usual treatment approach for this type of cancer. This study aims to assess if adding immunotherapy to these drugs is better or worse than the usual approach for treatment of this cancer.