Ovarian ablation (OA) in pre-menopausal women with early breast cancer prescribed 5 years tamoxifen (T) or T plus chemotherapy (CT)–results from the UK NCRI Adjuvant Breast Cancer (ABC) international trial of 2,144 patients

Abstract

535 Background: Substantial survival benefits are reported in women aged <50 with early stage ER positive breast cancer (BC) after OA as a single modality. The additional benefits of OA against a background of long term T or T plus CT in this group are unclear. Methods: The ABC trial is a pragmatic randomised phase III trial. One aspect of ABC compared OA (given as surgery, radiotherapy, or LHRH agonists) vs. none in patients diagnosed with early stage (1–3a) BC. All patients were prescribed 20mg T for 5 years. Elective CT was allowed. Main endpoints: relapse-free survival (RFS) and overall survival (OS). Results: During 1993 to 2000, 2144 (1063 OA, 1081 no OA) patients were randomised from 106 UK and 16 non-UK centres. Pre-treatment characteristics were well-balanced. In total 61% patients were age 41–50 years, 64% node positive, and 68% oestrogen receptor (ER) positive. 89% patients received OA as allocated. OA was given by radiotherapy (69%), surgery (23%) and LHRH agonists (8%). 80% patients received CT (mostly CMF). Results are based on median follow-up of 4.7 years, 565 relapses and 418 deaths. No statistically significant difference was seen in RFS (HR 0.98, 95%CI 0.83–1.16, p=0.81) or OS (HR 0.96, 95%CI 0.79–1.16, p=0.64). No differences were seen by adjustment or in subgroups based on age, nodal status or hormonal status. In addition there was no suggestion of a benefit in RFS (HR 0.95, 95%CI 0.62–1.43, p=0.80) or OS (HR 1.04, 95%CI 0.62–1.73, p=0.88) in the 427 patients randomised against a background of T alone. Conclusion: In this first study to report the added impact of adjuvant OA against a background of 5 years T, no effect of OA on RFS or OS was seen overall or in any sub-group taking 5 years T. No significant financial relationships to disclose.