Adjuvant radiation therapy is associated with improved overall survival in high-intermediate risk stage I endometrial cancer: A national cancer data base analysis

Purpose. Adjuvant radiation therapy (RT) was shown to improve local control in patients with high-intermediate risk (HIR) stage I endometrial cancer (EC) in randomized trials. Overall survival (OS) was not significantly different with adjuvant RT in these trials or subsequent meta-analyses; however, they were underpowered to assess OS. We used the National Cancer Data Base (NCDB) to examine the impact of adjuvant RT on OS in HIR EC patients. Methods. The NCDB was queried for patients diagnosed with FIGO (2009) Stage I endometrioid adenocarcinoma from 1998 to 2012 who underwent surgery +/- adjuvant RT. Per ASTRO guidelines, HIR risk was defined as stage IB and/or grade 3. Patients were excluded if: non-surgical primary therapy, RT > 180 days after surgery, unknown stage/grade/RT status, or RT to targets outside pelvis/vagina. Kaplan-Meier plots and Cox proportional hazards regression were used. Results. 33,600 patients met criteria. 18,070 patients (53.8%) received surgery alone, 15,530 patients (462%) received surgery + adjuvant RT. Of patients who received adjuvant RT, 42.2% received external beam RT, 44.7% brachytherapy, and 13.1% received both. 5-year OS was 79.2% for the surgery alone group and 83.3% for the surgery + adjuvant RT (p < 0.0001). On multivariate analysis, adjuvant RT was independently associated with improved OS vs. surgery alone (HR 0.7; 95% CI 0.8-0.9, p < 0.0001). Conclusions. Our results show that surgery + adjuvant RT was associated with a statistically significant 4.1% improvement in 5-year OS vs. surgery alone in stage I HIR EC. This data along suggests that the improvement in local control with adjuvant RT leads to improved OS. Published by Elsevier Inc.