Adjuvant external beam radiotherapy (EBRT) in the treatment of endometrial cancer: Results of the randomised MRC ASTEC and NCIC CTG EN.5 trial

5504 Background: Patients with stage I endometrial cancer at high risk of relapse generally receive adjuvant EBRT following surgery, despite lack of evidence that radiotherapy improves overall survival (OS). ASTEC/EN.5 was designed to investigate whether OS is improved by adjuvant EBRT. An important secondary outcome was pelvic recurrence-free survival. Methods: Patients were randomised to receive immediate EBRT (with linear accelerator delivering 40–46Gy in 20–25 fractions to pelvis) or no EBRT until clinically indicated. Vault brachytherapy (4Gy in 2 fractions (HDR) or 15Gy (LDR)) could be used regardless of EBRT allocation. Centers were required to specify in advance whether brachytherapy would be offered to all patients or to none. The study was powered both to 1) detect a 9–10% absolute improvement in 5-year OS with adjuvant EBRT; and 2) reliably exclude an absolute 5% difference in 5-year OS when combined with other major studies (PORTEC and GOG 99). Results: Between Oct 1996 to Apr 2005, 906 patien...