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

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. 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. 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. 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. •This population-based study investigated adjuvant therapy in stage III endometrial cancer.•Survival after external beam radiotherapy (EBRT) and chemotherapy (CT) was superior to that after CT and radiotherapy alone.•Patients with stage IIIC endometrioid tumours or carcinosarcomas benefited most from EBRT + CT.•EBRT + CT was not superior to CT or radiotherapy alone in stage IIIA/B or serous tumours.