A new analysis of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, presented at the 11th International St Gallen Oncology Conference, Switzerland, shows that during the first two years after surgery, anastrozole is superior to tamoxifen at reducing the risk of breast cancer returning in postmenopausal women with hormone receptor positive early breast cancer (n=5,216). Anastrozole has consistently demonstrated superiority over tamoxifen, both during the five-year treatment period and beyond treatment completion. This latest analysis provides further reassurance that prescribing anastrozole from the start protects women in the crucial first two years when the risk of recurrence is highest, meaning that fewer patients have to be told the devastating news that their breast cancer has returned.

When breast cancer returns, particularly outside the breast at distant sites such as bone, liver or lung, it is no longer curable. Therefore protecting women from recurrence is the number one priority for doctors and is imperative to saving lives. Although the risk of recurrence can persist for up to at least 15 years, the risk is at its greatest within the first two years following surgery, as seen in the ATAC study where over half of all excess recurrences and deaths among patients taking tamoxifen occurred in the first two and a half years.

This latest analysis confirms that in women who benefit from treatment with AIs (84 per cent of the total ATAC population) anastrozole is even more effective at preventing all types of early recurrence (32 per cent; two years post surgery) than previously seen in the broader study population (17 per cent; 2.5 years post surgery).

Professor Howell continued, "It is now standard practice to assess the hormone receptor status of breast tumours to guide the best course of treatment. ATAC is a ground breaking study which has led to a significant change in treatment strategies in breast cancer with aromatase inhibitors, such as anastrozole, now replacing tamoxifen as the standard of care for postmenopausal women with hormone receptor positive disease in many countries. These new findings confirm that in the women who receive it in routine clinical practice, anastrozole offers reassuring protection against their cancer returning at the time of greatest risk, giving women the best chance of continuing their lives cancer-free."

The ATAC trial is one of the world's largest and longest-running clinical studies in postmenopausal women with early breast cancer. With a median follow-up of 100 months - significantly longer than any other adjuvant AI trial - ATAC provides further information on the safety profile of anastrozole which remains predictable, with no long-term safety concerns. As a result of the weight of efficacy and safety evidence for anastrozole, it is now the most widely prescribed AI worldwide, with over twice as many prescriptions as the next most widely prescribed AI and over 4 million patient years' experience. These new data will offer doctors treating hormone receptor positive postmenopausal early breast cancer further confidence that initial treatment with anastrozole offers women the best chance of staying recurrence free.

The Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial is one of the world's largest and longest-running clinical studies in postmenopausal women with early breast cancer.