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>180days 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 (46.2%) 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.
Keywords: Adjuvant therapy; Endometrial cancer; Intermediate risk; NCDB; Radiotherapy.
Published by Elsevier Inc.