Fast track — ArticlesEffect of anastrozole and tamoxifen as adjuvant treatment for early-stage breast cancer: 10-year analysis of the ATAC trial
Introduction
Previous reports from the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial1, 2, 3 have shown significantly prolonged disease-free survival, lower rates of recurrence and distant recurrence, and significantly reduced contralateral breast cancer in patients treated with anastrozole compared with tamoxifen. Additionally, anastrozole was associated with significantly fewer serious adverse events than tamoxifen, including fewer patients with endometrial cancer, but increased numbers of fractures and reports of arthralgia during treatment.4 Dowsett and colleagues5 have summarised the role of aromatase inhibitors, such as anastrozole, in the adjuvant treatment of early breast cancer.
A 10-year median follow-up of the ATAC trial was completed to satisfy a US Food and Drug Administration requirement for updated efficacy and safety information. This analysis provided about 13 months of additional follow-up data beyond the previously published 100-month follow-up report,3 but only assessed disease-free survival, time to recurrence, overall survival, and safety for all patients. Here, we extend this analysis to include also time to distant recurrence and incidence of contralateral breast cancer, and report the updated data from the ATAC trial at 120 months follow-up.
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Patients and procedures
The ATAC trial has been described in detail previously.6 Briefly, eligible patients were postmenopausal women with histologically proven operable invasive breast cancer. Patients were randomly assigned (1:1:1) to receive active anastrozole plus tamoxifen placebo, active tamoxifen plus anastrozole placebo, or active anastrozole plus active tamoxifen. Anastrozole was given as 1 mg and tamoxifen as 20 mg daily oral tablets for 5 years. The combination treatment group was discontinued after the
Results
Median follow-up for this analysis was 120 months (range 0–145). This follow-up included a total of 48 473 women-years of follow-up (24 522 woman-years for anastrozole and 23 950 woman-years for tamoxifen). Baseline characteristics have been described previously;6 the median age at this analysis was 72 years (IQR 65–91).
Table 1 summarises the results for all efficacy endpoints for all randomised patients and the hormone-receptor-positive subgroup. Overall, hazard ratios were similar to those in
Discussion
This 10-year analysis of the ATAC trial confirms the previously reported efficacy and tolerability benefits of anastrozole as initial adjuvant therapy for postmenopausal women with early hormone-receptor-positive breast cancer (panel; table 4). Tamoxifen has shown a carryover benefit for recurrence in the first 5 years after treatment, but not after that.9 This so-called carryover effect for recurrence was larger for anastrozole than for tamoxifen in the present study and remained significant
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