New data establish Arimidex as superior to tamoxifen in preventing breast cancer recurrence

December 8, 2004 -- New data, from the landmark ATAC (Arimidex', Tamoxifen, Alone or in Combination) trial, were presented at the San Antonio Breast Cancer Symposium, in Texas. These definitive data show that in postmenopausal women with hormone sensitive, early breast cancer, AstraZeneca's treatment, Arimidex (anastrozole), reduces the risk of breast cancer returning by an additional 26 per cent over and above the 50 per cent reduction in risk already offered by tamoxifen. These data also conclude that Arimidex' is associated with fewer life threatening side effects than those seen with tamoxifen, particularly blood clots, stroke and cancer of the womb lining.

The greatest fear for women who have been treated for early stage breast cancer is to have their cancer return. Experts agree that the first five years following primary surgery is when women are at greatest risk of their disease returning.

"It is critical that women get the best treatment option available to them at the earliest opportunity after diagnosis to minimise the risk of recurrence," said Professor John Forbes of Newcastle Mater Misericordiae Hospital, Australia.

Data from the ATAC trial now conclusively demonstrate that Arimidex provides women with even greater protection than tamoxifen by reducing the risk of breast cancer recurrence by over half as much again. As a result, more women can live cancer free. A reduction in this risk of recurrence is associated with an improvement in overall survival; Arimidex offers women the best possible chance to stay alive and cancer free.

Professor John Forbes added, "Quite simply, if breast cancer does not return, women will not die from it. With tamoxifen, many women have had to live with the risk that their breast cancer could come back, even before they have completed their course of treatment. Now, for the first time in 30 years, we have a drug that is better than tamoxifen to fight breast cancer - anastrozole."

Arimidex is the only drug of its type to have extensive safety data with over five years of clinical experience in early breast cancer. Tolerability is of primary concern for women with early breast cancer and for clinicians treating them. These data show that Arimidex is better tolerated than tamoxifen, both for serious life threatening side effects and other side effects affecting quality of life. Women taking Arimidex in the ATAC trial experienced more fractures and joint pain than those receiving tamoxifen, which is known to have a positive effect on bone mineral density. However, the side effects of Arimidex are considered more predictable and manageable than some of the serious side effects commonly associated with tamoxifen. Additionally, as a result of the better tolerability profile, women on Arimidex were more likely to stay on therapy for longer than those on tamoxifen.

The vast majority of patients in the ATAC trial have completed five years of treatment and these data are now considered conclusive. Breast cancer specialists believe that anastrozole should replace tamoxifen as the preferred initial hormonal treatment, in order to provide women with the best possible chance of staying free of their disease.

About the ATAC trial

The ATAC trial is the largest and longest running early breast cancer treatment study. The trial reports data from over 9,300 postmenopausal women with early breast cancer who took either anastrozole or tamoxifen once per day for five years following their initial breast cancer surgery. This latest analysis compares the two groups of women once the majority had completed their treatment. The new data show that anastrozole reduces the risk of all forms of breast cancer recurrence by an additional 26 per cent over and above that offered by tamoxifen. Furthermore, anastrozole provides an additional 16 per cent reduction in the risk of the disease spreading to other parts of the body, compared to tamoxifen.

The ATAC trial compares five years of treatment with tamoxifen to five years of treatment with anastrozole, in women newly diagnosed with early breast cancer. Eighty-four per cent of patients in the trial had tumours which are known to respond to hormonal treatment.

Source: AstraZeneca

Posted: December 2004


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