Adjuvant brachytherapy for FIGO stage I serous or clear cell endometrial cancer

OBJECTIVES: Optimal adjuvant treatment for early-stage clear cell and serous endometrial cancer remains unclear. We report outcomes for women with surgically staged International Federation of Gynecology and Obstetrics (FIGO) stage I clear cell, serous, and mixed endometrial cancers following adjuvant vaginal cuff brachytherapy with or without chemotherapy. METHODS: From April 1998 to January 2020, women with FIGO stage IA–IB clear cell, serous, and mixed endometrial cancer underwent surgery and adjuvant vaginal cuff brachytherapy. Seventy-six patients received chemotherapy. High-dose rate vaginal cuff brachytherapy was planned to a total dose of 21 gray in three fractions using a multichannel vaginal cylinder. The primary objective was to determine the effectiveness of adjuvant vaginal cuff brachytherapy and to identify surgicopathological risk factors that could portend towards worse oncological outcomes. RESULTS: A total of 182 patients were included in the analysis. Median follow-up was 5.3 years (2.3–12.2). Ten-year survival was 73.3%. Five-year cumulative incidence (CI) of vaginal, pelvic, and para-aortic relapse was 1.4%, 2.1%, and 0.9%, respectively. Five-year locoregional failure, any recurrence, peritoneal relapse, and other distant recurrence was 4.4%, 11.6%, 5.3%, and 6.7%, respectively. On univariate analysis, locoregional failure was worse for larger tumors (per 1 cm) (HR 1.9, 95% CI 1.2 to 3.0, p≤0.01). Any recurrence was worse for tumors of at least 3.5 cm (HR 3.8, 95% CI 1.3 to 11.7, p=0.02) and patients with positive/suspicious cytology (HR 4.4, 95% CI 1.5 to 12.4, p≤0.01). Ten-year survival for tumors of at least 3.5 cm was 56.9% versus 86.6% for those with smaller tumors (HR 2.9, 95% CI 1.4 to 5.8, p≤0.01). Ten-year survival for positive/suspicious cytology was 50.9% versus 77.4% (HR 2.2, 95% CI 0.9 to 5.4, p=0.09). Multivariate modeling demonstrated worse locoregional failure, any recurrence, and survival with larger tumors, as well as any recurrence with positive/suspicious cytology. Subgroup analysis demonstrated improved outcomes with the use of adjuvant chemotherapy in patients with large tumors or positive/suspicious cytology. CONCLUSION: Adjuvant vaginal cuff brachytherapy alone without chemotherapy is an appropriate treatment for women with negative peritoneal cytology and small, early-stage clear cell, serous, and mixed endometrial cancer. Larger tumors or positive/suspicious cytology are at increased risk for relapse and worse survival, and should be considered for additional upfront adjuvant treatments, such as platinum-based chemotherapy.