Defining the survival benefit of adjuvant pelvic radiotherapy and chemotherapy versus chemotherapy alone in stages III-IVA endometrial carcinoma.

OBJECTIVES: To determine which patients with locoregionally advanced endometrial cancer may benefit from pelvic external beam radiotherapy (EBRT) in addition to chemotherapy compared to chemotherapy alone.

METHODS: Patients with FIGO stages III-IVA endometrial carcinoma between 2004 and 2016 who underwent at least total hysterectomy and adjuvant multiagent chemotherapy were identified in the National Cancer Database. The primary outcome was overall survival according to receipt of pelvic EBRT, analyzed using the Kaplan-Meier method and Cox multivariable regression.

RESULTS: In total, 13,270 patients were identified (62% pure endometrioid, 38% serous/clear cell or mixed histology; 22.6% stage IIIA, 4.7% stage IIIB, 71.2% stage IIIC, 1.5% stage IVA), of whom 40% received pelvic EBRT. In univariable analysis, EBRT was associated with absolute 5-year survival increases of 5% and 9% in the endometrioid and non-endometrioid cohorts, respectively (P < 0.0001). In multivariable analyses stratified by stage and histology, patients with a significant benefit from EBRT were stage IIIC (specifically IIIC2) endometrioid (adjusted hazard ratio [HR] 0.73, P = 0.01) and stages IIIB and IIIC non-endometrioid (adjusted HR 0.52, P = 0.01 and adjusted HR 0.79, P < 0.0001). The benefit of EBRT in node-positive patients persisted in those who underwent more extensive lymphadenectomy.

CONCLUSIONS: Stages III-IVA endometrial cancer comprised a heterogeneous population with respect to the added benefit of radiotherapy compared to chemotherapy alone. Patients with stage IIIC2 endometrioid and stages IIIB-C non-endometrioid cancer may be most likely to benefit from pelvic EBRT.