A longitudinal study of the adherence to PORTEC-2 based adjuvant radiotherapy in high-intermediate-risk endometrial adenocarcinoma and associated oncologic outcomes.

Abstract

e17570 Background: In 2010, Nout et al. reported on PORTEC-2, which randomized patients with high intermediate risk (HIR) endometrial cancer to adjuvant vaginal brachytherapy or pelvic radiotherapy or observation, and showed that vaginal brachytherapy was non-inferior in terms of locoregional control and was deemed the adjuvant treatment of choice for these patients. We sought to evaluate the adherence to and the oncologic outcomes of the PORTEC-2 regimen. Methods: We utilized the SEER database to identify patients who met PORTEC-2 inclusion criteria. All patients underwent surgery followed by either vaginal brachytherapy (VBT) or whole pelvic radiotherapy (WPRT). Inclusion criteria were patients with the following characteristics: grade 1 with ≥ 50% myometrial invasion (MI), grade 2 with any invasion, and grade 3 with < 50% MI. Patients were excluded if any lymph nodes were examined or involved, if they received any chemotherapy, or had any missing values for any of the variables. HIR endometrial adenocarcinoma was defined as the presence of 2 of the following: age > 60, grade 3, and ≥50% myometrial invasion. Radiation status was extracted from the SEER Radiation/Chemotherapy database. Outcomes were overall death, cancer specific death and total survival months per SEER’s standard definitions. Variables are reported as median and interquartile range (IQR) or number (%). Mean survival was calculated using Kaplan Meier analysis and Mantel-Cox rank test was done to test for statistical significance between the study groups. Cox regression analysis was performed, and hazard ratios (HR) were calculated. Statistical analysis was performed using SPSS v. 22.0. Results: Between 2005- 2015, 571 patients met PORTEC-2 inclusion criteria of whom 349 (61.1%) and 222 (38.9%) received WPRT and VBT, respectively. We showed that the rate of VBT was significantly increased from 85 (27.4%) between 2005-2010 to 137 (52.5%) between 2011-2015 (p < 0.001). There was no difference in grade and myometrial invasion between the study groups. Kaplan Meier analysis showed a 22.5 and 16.3 month improvement in overall and cancer specific survival in subjects who underwent VBT as compared to WPRT, respectively (p < 0.001 for both). Cox regression analysis revealed a 36% and 66% decrease in the hazard of overall and cancer specific death, respectively, in the VBT group as compared to WPRT group (Overall death: HR = 0.64, 95% CI: 0.45-0.91, p = 0.012; Cancer specific death: HR = 0.34, 95% CI: 0.16-0.73, p = 0.006). Conclusions: Administration of vaginal brachytherapy following surgery has become significantly more popular after publication of the PORTEC-2 results in 2010. Our study shows a significant decrease in both overall and cancer related death and an increase in survival with VBT over WPRT in patients with HIR endometrial cancer.