Background: Survival of patients with early-stage breast cancer is improved following treatment with single-modality tamoxifen, ovarian ablation or suppression, or chemotherapy. The Adjuvant Breast Cancer Trials were designed to ascertain any additional benefits of combined treatment. Methods: The Adjuvant Breast Cancer Chemotherapy Trial was a randomized phase III trial in which patients with early-stage breast cancer who were receiving prolonged (5 years) tamoxifen treatment, with or without ovarian ablation or suppression, were randomly assigned to standard chemotherapy versus none. Trial endpoints included relapse-free and overall survival. Hazard ratios (HRs) were derived from Cox models, and all statistical tests were two-sided. Results: Between 1992 and 2000, 1991 patients between the ages of 26 and 81 years were randomly assigned (987 to chemotherapy, 1004 to no chemotherapy) from 106 UK and 16 non-UK centers. Nine hundred seven (92%) patients received chemotherapy as allocated (87% received cyclophosphamide, methotrexate, and 5-fluorouracil; 11% received anthracycline-containing regimens). A total of 244 of the 619 premenopausal patients received elective ovarian ablation or suppression. Chemotherapy improved relapse-free survival (relapse in the chemotherapy group versus no-chemotherapy group, 298 events versus 332 events, HR = 0.86, 95% confidence interval [CI] = 0.73 to 1.01; P = .06) and overall survival (death from any cause in the chemotherapy group versus no-chemotherapy group, 243 events versus 282 events, HR = 0.83, 95% CI = 0.70 to 0.99; P = .03) after adjustment for nodal status, estrogen receptor status, and age. Subgroup analyses showed that the benefit of chemotherapy was greatest in younger women (<50 years) and in particular for premenopausal women not receiving ovarian ablation or suppression. Conclusion: Modest yet sustainable benefits for chemoendocrine therapy occur in women with breast cancer. However, the full impact on overall survival may not emerge for several years. © 2007 The Author(s).
