CLINICAL TRIAL / NCT04683653

Inclusion Criteria: - Diagnosis of endometrial cancer with any of the following primary histologic types: endometrioid, papillary serous, clear cell, carcinosarcoma, or mixed epithelial histologies. - Age ≥ 18 years. - Must have been diagnosed with Stage I-III disease according to The International Federation of Gynecology and Obstetrics (FIGO). - Must have been treated with definitive intent, including standard-of-care hysterectomy, without any gross residual disease post-operatively. Nodal dissection is not required, but if it is not performed, then diagnostic imaging to confirm absence of gross pelvic or para-aortic disease should be obtained pre- or post-operatively. - Recommended to undergo whole pelvic radiotherapy without concurrent chemotherapy or para-aortic radiation. Chemotherapy before or after radiotherapy is acceptable. Exclusion Criteria: - Distant metastases as determined clinically or radiographically based upon standard-of-care work-up for endometrial cancer. - Concurrent (or other) chemotherapy occurring at the time of study. - Gross residual disease (cancer cells that remain after attempts to remove the cancer have been made) post-operatively and/or at the time of radiation based upon pre-op or post-op imaging, intra-operative findings, and gynecologic oncologists' judgment. - History of small bowel obstruction, inflammatory bowel disease, irritable bowel syndrome, connective tissue disorder requiring ongoing active medical management, or prior radiation therapy directed to the pelvis. - Unresolved chemotherapy-associated diarrhea or abdominopelvic pain requiring medication prior to the initiation of radiation. - Recommendation to undergo para-aortic nodal irradiation.