A Study of Short-Course Radiation Therapy With Chemotherapy in People With Endometrial Cancer

Inclusion Criteria: * Patients must have newly diagnosed endometrial carcinoma. The following histologic subtypes are eligible for inclusion: endometrioid, serous, clear cell, dedifferentiated/undifferentiated, mixed epithelial, adenocarcinoma not otherwise specified, and carcinosarcoma. * Surgery must have included a hysterectomy, bilateral salpingo-oophorectomy, and pelvic lymph node surgical assessment (sentinel lymph node mapping and/or sampling). Para-aortic lymph node surgical assessment is optional. * Patients must have FIGO (2009) stage IIIA or IIIC1 disease (as determined by surgical staging). * Patients must consent to testing with MSK-IMPACT part A and are encouraged to consent to both parts A and C. * Age ≥ 18 years. * Patients must have an Karnofsky Performance Status (KPS) ≥ 70 (or ECOG 0 or 1). * Neurologic function: Neuropathy (sensory and motor) grade ≤ 1. * No residual gross disease after surgery. * No prior radiation therapy or chemotherapy for treatment of endometrial cancer. * No active infection requiring antibiotics, except for uncomplicated urinary tract infection. * Patients must have adequate organ function, defined by the following laboratory results no more than 14 days prior to first study treatment: * Absolute neutrophil count (ANC) ≥ 1500/mcL * Platelet count ≥ 100,000/mcL * AST/ALT ≤ 3X upper limit of normal (ULN) * Total bilirubin ≤ 1.5X ULN. Patients with known Gilbert's disease and a total bilirubin ≤ 3X ULN may be enrolled. * Cr…