To evaluate whether the addition of radiation to adjuvant chemotherapy is associated with improved survival in women with stage IV endometrial cancer following surgery.

The National Cancer Database (NCDB) and Surveillance, Epidemiology, and End Results Program (SEER) registries were queried for patients with stage IV endometrial cancer from 2004 to 2017. Treatment was categorized as chemotherapy alone, chemotherapy with external beam radiation therapy (EBRT), chemotherapy with vaginal brachytherapy (VBT), or chemotherapy with EBRT+VBT. Multivariable Cox regression models assessed associations between treatment modality and overall survival (OS).

This analysis included 17,890 (NCDB: 12,812, SEER: 5078) women with stage IV endometrial cancer, including 1757 (9.8%) with IVA disease and 16,133 (90.2%) with IVB. The majority of stage IV patients received chemotherapy alone (NCDB 78.8%, SEER 77.0%). When radiation was utilized in addition to chemotherapy, EBRT was most common (NCDB 15.8%, SEER: 15.4%). In both databases, use of any radiation in addition to chemotherapy was associated with improved OS. Stage IV patients treated with chemotherapy plus EBRT had better survival than those receiving chemotherapy alone [NCDB: HR 0.75 (95% CI 0.70, 0.79), SEER: HR 0.85 (95% CI 0.77, 0.94)]. This benefit was more pronounced in patients with IVA disease [NCDB: HR 0.66 (95% CI 0.55, 0.79), SEER: HR 0.63 (95% CI 0.46, 0.85)]. In histology-stratified analyses, the addition of radiation to chemotherapy was associated with improved OS in all histologies, except clear cell.

In this analysis of the NCDB and SEER registries, the use of multimodality treatment with radiation and chemotherapy was associated with improved OS compared to chemotherapy alone in women with stage IVA and IVB endometrial cancer.