Polychemotherapy (CT) in pre- and post-menopausal women with early breast cancer prescribed 5 years tamoxifen (T) –results from the UK NCRI Adjuvant Breast Cancer (ABC) international trial in 1991 patients

Abstract

656 Background: EBCTCG 2000 systematic overview confirmed overall survival advantage of CT in early breast cancer (BC), but doubts remain over these benefits in presence of concomitant prolonged tamoxifen (T) and ovarian ablation (OA) in premenopausal women. Methods: The ABC trial is a pragmatic, randomised phase III trial. One aspect of ABC compared CT (any type but CMF recommended) vs. none in patients with early (1–3a) BC. All patients prescribed 20mg T for 5 years. Patients could receive OA or not as elective treatment. Main endpoints: relapse-free survival (RFS) and overall survival (OS). Results: During 1993 to 2000, 1991 (987 CT, 1004 no CT) patients were randomised from 106 UK and 16 non-UK centres. Pre-treatment patient characteristics were well-balanced. In total 62% patients were age >50 years, 56% node positive, and 64% oestrogen receptor (ER) positive. 92% patients received CT as allocated. Type of CT was CMF (87%), anthracycline containing (11%). 244 patients received OA. Results based on median follow-up of 5.0 years, 601 relapses and 485 deaths. CT suggested an improvement in RFS (HR 0.86 [95%CI 0.73–1.01] p=0.061) and OS (HR 0.87 [95%CI 0.73–1.04] p=0.12) but unadjusted results did not reach conventional levels of statistical significance. Adjusting for nodal status, ER, age, OA slightly increases magnitude of benefit of CT (RFS: HR 0.83 (0.71–0.97) p=0.024, OS: HR0.84 (0.70–1.00) p=0.051). Results (RFS) were independent of ER status. Impact appeared greater for women aged <50 (<50 HR 0.76 [0.57–1.01], ≥50 HR 0.89 [0.73–1.09]), for those (pre-menopausal) not receiving OA (without OA HR 0.71 [0.47–1.08], with OA HR 0.94 [0.56–1.56]) and for those from centres with good CT compliance (good CT HR 0.83 [0.68–1.01], poor CT HR 0.95 [0.71–1.25]). Conclusion: This is the first report of CT in women with early BC receiving concomitant and 5-year duration T, showing that benefits of CT are retained in this context. No significant financial relationships to disclose.