Title: A Multicenter, Open-label, Randomized, Phase 3 Trial to Compare the Efficacy and Safety of Lenvatinib in Combination with Pembrolizumab Versus Treatment of Physicians Choice in Participants with Advanced Endometrial Cancer; Description: This is a study of pembrolizumab (MK-3475, KEYTRUDA) in combination with lenvatinib (E7080) versus treatment of physicians choice (doxorubicin or paclitaxel) for the treatment of advanced endometrial cancer. Participants will be randomly assigned to receive either pembrolizumab and lenvatinib or treatment of physicians choice. The primary study hypothesis is that pembrolizumab in combination with lenvatinib prolongs progression free survival (PFS) and overall survival (OS) when compared to treatment of physicians choice. ; 4 Key Inclusion/Exclusion Criteria including Age Range If Applicable: Inclusion Criteria- 1. Has a histologically confirmed diagnosis of endometrial carcinoma (EC) and documented evidence of advanced, recurrent or metastatic EC. 2. Has radiographic evidence of disease progression after 1 prior systemic, platinum-based chemotherapy regimen for recurrent, metastatic or primary unresectable disease. 3. Has historical or fresh tumor biopsy specimen for determination of mismatch repair (MMR) status. 4. Has at least 1 measurable target lesion according to Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 and confirmed by Blinded Independent Central Review BICR. Ages Eligible for Study: 18 Years and older Exclusion Criteria- 1. Has carcinosarcoma (malignant mixed mullerian tumor), endometrial leiomyosarcoma and endometrial stromal sarcomas. 2. Has unstable central nervous system (CNS) metastases. 3. Has active malignancy (except for endometrial cancer, definitively treated in-situ carcinomas e.g. breast, cervix, bladder, or basal or squamous cell carcinoma of the skin) within 24 months of study start. 4. Has gastrointestinal malabsorption, gastrointestinal anastomosis, or any other condition that might affect the absorption of lenvatinib.