Anthony Howell, MD, professor of medical oncology, University of Manchester, Manchester, United Kingdom, and associates reported findings from a combined analysis of the efficacy, safety, and tolerability events after 68 months of follow-up in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial.

The analysis aimed to provide an overall index of the risks versus benefits of treatment with anastrozole compared with tamoxifen, Dr. Howell said on October 31^st.

The ATAC trial compared the efficacy and tolerability of anastrozole and tamoxifen for the adjuvant treatment of postmenopausal women with early breast cancer. Results in 9366 women at a median follow-up of 68 months bolstered earlier analyses and showed that anastrozole is significantly more effective than tamoxifen in preventing recurrences.

In addition, the analysis showed that there were significantly fewer withdrawals due to adverse events and treatment-related serious adverse events in the anastrozole group than in the tamoxifen group.

Two global risk:benefit indices were constructed. The first global index used the Women's Health Initiative definition of events and was defined as the time from randomization to the earliest occurrence of breast cancer recurrence, death, or a life-threatening adverse event. A second index modified to include breast-cancer-related events was developed based on the time to recurrence, death, or any serious adverse event.

The investigators mapped the ATAC adverse events to the adverse event terms used by the Women's Health Initiative.

Results showed that treatment-related adverse events were significantly less common with anastrozole (60.9% vs 68.4%, risk ratio [RR] =.89).

On-treatment serious adverse events were also significantly less common with anastrozole than tamoxifen (33.3% vs 36.0%, RR =.93), as were treatment-related serious adverse events (4.7% vs 9.0%, respectively, RR =.53).

"Our analysis of the data from the ATAC trial using 2 global indices has thus demonstrated a superior risk:benefit profile for anastrozole compared with tamoxifen," Dr. Howell said.


[Presentation title: Global Index to Summarize Health Risks Versus Benefit in the ATAC (Arimidex, Tamoxifen, Alone or in Combination) Trial. Abstract 349]

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