National patterns of care and cancer-specific outcomes of adjuvant treatment in patients with serous and clear cell endometrial carcinoma

Abstract Objectives To investigate outcomes of adjuvant therapy for serous and clear cell endometrial carcinoma, as prior studies are limited by sample size and/or patient heterogeneity. National guidelines permit substantial variations in treatment, suggesting the need for additional data. Methods Patients with FIGO stages I–III serous or clear cell uterine carcinoma who underwent at least total hysterectomy were identified in SEER-Medicare. Adjuvant external beam radiation, brachytherapy, and chemotherapy were determined using SEER fields and Medicare claims. The primary outcome was death from endometrial cancer (cancer-specific mortality [CSM]) evaluated using Gray's test (univariable analysis, UVA) and Fine-Gray regression (multivariable analysis, MVA). Results A total of 1789 patients (1437 serous, 352 clear cell) were identified. In stages I–II patients (n = 1188), brachytherapy was significant for survival in UVA ( P  = 0.03) and MVA ( P  = 0.02). Additionally, in the subset with serous histology (n = 947), chemotherapy was also significant in UVA ( P  = 0.002) and approached significance in MVA ( P  = 0.05). The 4-year CSM for stages I–II serous cancers was 25% without brachytherapy or chemotherapy, 15% with one, and 9% with both ( P  ≤ 0.05 for all pairwise comparisons). In stage III patients (n = 601), chemotherapy was significant in UVA ( P  = 0.002) and MVA ( P  = 0.006). Most (81%) patients underwent lymph node dissection, which predicted lower CSM in stage III ( P  = 0.001) but not stages I–II patients. Conclusions Our results suggest brachytherapy benefits stages I–II serous/clear cell cancers, chemotherapy benefits stage III serous/clear cell cancers, and both chemotherapy and brachytherapy benefit stages I–II serous cancers.