Racial Disparity in Accessibility and Outcomes of Adjuvant Radiotherapy in Stage I High Intermediate Risk Endometrial Adenocarcinoma: A National Database Study

Abstract

<h3>Purpose/Objective(s)</h3> Based on PORTEC-2 study in 2010, vaginal brachytherapy (VB) was found to be non-inferior to whole pelvic radiation (WPRT) in terms of survival and loco-regional control with a more favorable toxicity Profile. VB is now the preferred choice of adjuvant treatment in patients with high-intermediate risk (HIR) endometrial cancer, especially those with negative Lymphovascular space invasion. In this study we assessed the accessibility and outcomes of this recommended regimen in the different groups of race/ethnicity. <h3>Materials/Methods</h3> The Surveillance, Epidemiologic, and End Results (SEER) database was used to identify patients who met PORTEC-2 inclusion criteria. All patients underwent surgery followed by either vaginal brachytherapy (VB) or whole pelvic radiation (WPRT). Patients with stage I disease, grade 1 with ≥ 50% myometrial invasion (MI), grade 2 with any invasion, and grade 3 with < 50% MI were included in the analysis. Patients were excluded if any lymph nodes were examined or involved, if they received any chemotherapy. Lymphovascular space invasion was not available in the database. 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. Race/ethnicity was defined as non-Hispanic White (NHW), non-Hispanic Black (NHB), Hispanic and others/unknown. Cox regression analysis was performed to calculate hazard of cancer specific death and overall death both before and after counting for race/ethnicity with following variables in the model: grade, radiation status, myometrial invasion. <h3>Results</h3> Between 2005- 2015, 571 patients met PORTEC-2 inclusion criteria of whom 349 (61.1%) and 222 (38.9%) received WPRT and VB, respectively. Rate of VB was 38.9% overall, 41.1% in NHW however 29.0% in H and only 27.0% in NHB (p<0.05). There was no difference in grade and myometrial invasion between the study groups nor within categories of race/ethnicity (p=0.21 and 0.89, respectively). Cox regression analysis revealed an overall 66% decrease in the hazard of cancer specific death in the VB group as compared to WPRT group (HR=0.34, 95% CI: 0.16-0.73, p<0.01); this decrease was 67% in non-Hispanic White subjects (HR=0.33, 95% CI: 0.12-0.86, p<0.05) however no significant change was noted in NHB (HR=0.55, 95% CI: 0.11-2.67, p=0.45). Moreover, after adjusting for confounding variables, hazard of cancer specific death in NHB was 2.62 times higher than NHW (HR=2.62, 95% CI: 1.22-5.62, p=0.01). <h3>Conclusion</h3> Administration of VB following surgery has become significantly more popular after publication of the PORTEC-2 results however racial disparity exists against both accessibility to and outcomes of this treatment modality. Being a NHB is a risk factor for lack of accessibility as well as failure to respond to PORTEC-2 regimen; future studies on genetic predispositions are recommended.