Improved survival with adjuvant brachytherapy in stage IA endometrial cancer of unfavorable histology.

PURPOSE: We evaluated the utilization of vaginal brachytherapy (BT) and the resulting impact on survival in stage IA endometrial cancer of clear cell (CC), papillary serous (PS), and carcinosarcoma (CS) histology. METHODS: Patients with uterine cancer diagnosed from 2004 to 2015 were identified from the National Cancer Database. Patients underwent hysterectomy, showing FIGO stage IA disease with CC, PS, or CS histology. Logistic regression was used to evaluate predictors of BT utilization and to generate propensity scores. Survival was compared using log-rank test and Cox proportional hazards modeling, with propensity score adjustment. RESULTS: We identified 5711 patients who underwent hysterectomy showing FIGO pT1a, N0 or NX endometrial cancer with CC, PS, or CS histology, of which 29.5% received BT. Multivariate predictors of increased receipt of BT were identified. With a median follow-up of 3.3 years, 3-year overall survival (OS) was 87% for those receiving BT versus 78% for those without (p < 0.001). A survival benefit to BT was maintained across histologies. Similar results were seen whether tumor was confined to endometrium or had <50% myometrial invasion. On multivariate analysis, receipt of BT was associated with increased survival (hazard ratio [HR] 0.75, 95% confidence interval 0.65-0.87, p < 0.001). The benefit of BT persisted after propensity score adjustment (HR 0.76, p < 0.001). CONCLUSIONS: In this cohort of women with stage IA endometrial cancer of unfavorable histology, the use of BT was associated with improved survival. In this study, 29.5% of patients in our cohort received BT.