Impact of timing of adjuvant radiotherapy on locoregional control in patients with high-risk endometrial cancer

Aim: High-risk endometrial cancer has a higher risk of regional and distant recurrence. We sought to examine our institutional experience regarding the timing of adjuvant radiotherapy and local failure (LF), locoregional failure (LRF), distant failure (DF), and overall survival (OS). Methods: We retrospectively reviewed a database of patients with high-risk endometrial cancer treated with sequential chemotherapy followed by adjuvant external beam radiation therapy ( EBRT) with or without brachytherapy from 2012 to 2019.Results: One hundred thirty-one patients were identified. The median age at diagnosis was 65 (range 32-81). The most prevalent FIGO stages were IIIB (28.2%, n = 37), IIIC1 (19.8%, n = 26), and IIIA (17.6%, n = 23). Of the patients, 29% (n = 38) had positive lymph nodes and 71% (n = 93) had negative lymph nodes. The most prevalent histology was endometrioid (71%, n = 93), serous ( 12.2%, n = 16), clear cell (9.2%, n = 12), and other ( 7.6%, n = 10). Moreover, 100% ( n = 131) of the patients completed EBRT. The mean EBRT dose was 49.6 Gy (range 45-50.4). The median number of days between surgery and EBRT was 212.4 days (range 103- 219). The mean brachytherapy dose was 14.7 Gy (range 12-30). The cumulative incidence of LF was 6.1%, LRF was 19%, DF was 19%, and the median survival was 33.4 months. For patients who completed EBRT 180 days after surgery, LRF (HR 3.55 [1.23-10.2], P = 0.013), LF (HR 1.91 [0.4-8.9], P = 0.429), DF (HR 0.91 [0.41-2], P = 0.806), and OS (HR 0.92 [0.33-2.6], P = 0.87). Conclusion: In our cohort of patients with high-risk endometrial cancer treated with chemotherapy followed by radiotherapy, delaying RT was associated with an increased risk of LRF but no differences in DF or OS.