Impact of adjuvant chemotherapy prior to endocrine therapy: 68 month results from the ‘Arimidex’, Tamoxifen, Alone or in Combination (ATAC) trial

Abstract

608 Background: Previous analyses of the ATAC trial demonstrated initial adjuvant treatment with anastrozole (A) has significant efficacy and tolerability advantages over tamoxifen (T). At 33 months’ median follow-up there was a potential interaction with previous chemotherapy, which was less apparent at 47 months’ median follow-up. When the effects of different chemotherapy regimens were retrospectively evaluated at 47 months, the apparent interaction was limited to patients who had received cyclophosphamide, methotrexate and 5-fluorouracil (CMF). Here we evaluate the results from the ATAC trial at 68 months’ median follow-up to assess the effect of different chemotherapy regimens on time to recurrence (TTR) over the full 5-year treatment period. Methods: Chemotherapy regimens were (1) CMF, (2) anthracycline (AC)-containing regimens (AC, cyclophosphamide ± 5-fluorouracil), (3) other chemotherapies, including taxane-containing combinations. The impact of regimens on TTR was calculated and expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). Results: Consistent with the 47-month analysis, superiority for TTR was maintained for A versus T in the AC-containing and taxane-containing subgroups. Advantages for A are now evident with CMF. Adjusting for chemotherapy type had only a minimal effect on TTR. Conclusions: Despite the previously reported interaction within the CMF-group, additional follow-up has confirmed that the benefits of A over T are maintained regardless of the type of chemotherapy given. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration AstraZeneca AstraZeneca