Impact of different adjuvant treatment approaches on survival in stage III endometrial cancer: A population-based study

Background: Patients with International Federation of Gynaecology and Obstetrics (FIGO) stage III endometrial cancer (EC) have a substantial risk of adverse outcomes. After surgery, adjuvant therapy is recommended with external beam radiotherapy (EBRT), chemotherapy (CT) or both EBRT and CT. Recent trials suggest that EBRT + CT is superior to EBRT or CT alone but also results in more toxicity. We have compared the outcome of different adjuvant treatments in a population-based cohort to identify subgroups that benefit most from EBRT + CT. Methods: All patients diagnosed with FIGO stage III EC and treated with surgery in 2005-2016 were identified from the Netherlands Cancer Registry. The primary outcome was overall survival (OS); associations with adjuvant treatment were analysed using Cox regression analysis. Results: Among 1241 eligible patients, EBRT + CT was associated with a better OS than CT (hazard ratio [HR] = 1.84, 95% confidence interval [CI] = 1.34-2.52) and EBRT alone (HR = 1.37, 95% CI = 1.05-1.79). In stage IIIC, there was a significant benefit of EBRT + CT compared with CT or EBRT alone. In stage IIIA-B, there was no difference between EBRT + CT or EBRT alone. In endometrioid EC (EEC) and carcinosarcomas, EBRT + CT was associated with a better OS than CT or EBRT alone. For uterine serous cancers, there was no survival benefit of EBRT + CT over CT. In all analysis by stage and histology, any adjuvant treatment was superior to no adjuvant therapy. Conclusions: In this population-based study, adjuvant EBRT + CT was associated with improved OS compared with CT or EBRT alone in FIGO stage IIIC EC, EEC and carcinosarcoma. This suggests that application of EBRT + CT in stage III should be further stratified according to these subgroups. (C) 2020 The Author(s). Published by Elsevier Ltd.