Patterns of Care in Adjuvant Radiation Therapy for Stage II Endometrioid Endometrial Adenocarcinoma: A National Cancer Database Analysis

Purpose: Treating stage II endometrial cancer involves total hysterectomy, bilateral salpingo-oophorectomy, and risk-adapted adjuvant therapy. Professional guidelines support various adjuvant treatments, but high-level data supporting specific options are conflicting. We sought to evaluate adjuvant radiation therapy (RT) trends for these patients, hypothesizing increased utilization of pelvic external beam RT (EBRT) over time. Methods and Materials: Patients diagnosed in 2004-2019 with stage II endometrioid endometrial cancer who underwent total hysterectomy, bilateral salpingo-oophorectomy, and surgical staging were identified in the National Cancer Database. Patient characteristics per adjuvant RT received were compared using Wilcoxon rank sum and analysis of variance testing. Multivariable regression analysis (MVA) identified variables associated with EBRT, vaginal brachytherapy (VBT), or RT omission. A P value < .05 was significant, except in MVA, where Bonferroni correction was employed (p value < .017). Results: Patients meeting criteria totaled 18,798; 19% received adjuvant EBRT alone, 25% VBT alone, 24% EBRT + VBT, and 32% no RT. Adjuvant RT use increased from 2004 to 2019, particularly EBRT + VBT (p < .05). In MVA, community hospital treatment (odds ratio [OR], 1.8; p < .001), Midwest location (OR, 1.2; p = .02), single-agent chemotherapy receipt (OR, 6.9; p < .001), lymphovascular space invasion (OR, 1.4; p < .001), and positive surgical margins (OR, 1.8; p < .001) were positively associated with EBRT. No variables were positively associated with VBT. Black race (OR, 1.2; p = .03), community hospital treatment (OR, 1.4; p = .04), South (OR, 2.2; p < .001) or West (OR, 2.1; p < .001) location, distance >50 miles from the treatment center (OR, 1.5; p < .001), and grade 2 (OR, 1.2; p < .001) or 3 (OR, 1.3; p = .01) disease were associated with RT omission. Conclusions: Adjuvant RT for stage II endometrial cancer increased over time, particularly EBRT + VBT. Patient-related factors such as race, region, and distance from the treatment center were associated with RT omission, suggesting sociodemographic barriers to care. Tumor-related factors such as positive surgical margins and lymphovascular space invasion were associated with EBRT receipt, suggesting consideration of high-risk factors for locoregional recurrence in adjuvant RT approaches.