About IBIS-II Prevention

1. Background to the Study
2. IBIS-II Study
3. Why investigate anastrozole in the prevention of breast cancer?
4. Examining anastrozole’s effect on women’s bones
5. Who can take part

Why investigate anastrozole in the prevention of breast cancer?

• Recent research has shown that anastrozole is more effective than tamoxifen at preventing the return of cancer in post-menopausal women who have an early breast cancer removed. In these women it reduces their risk of developing a new cancer in the opposite (contralateral) breast by 53% compared to tamoxifen¹.
• This is a very strong indicator that anastrozole will be more effective than tamoxifen in preventing breast cancer in women who have not yet developed the disease.
• Research has also shown that anastrozole has fewer serious side effects than tamoxifen, which can cause womb cancer and blood clots. Anastrozole does have some side effects such as hot flushes, vaginal dryness and an increase risk of osteoporosis¹.
• This supporting evidence has led to the start of the IBIS-II prevention study, a trial to investigate whether anastrozole could prevent also breast cancer but with fewer side effects than tamoxifen.

1. ATAC Trialists' Group. Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 years' adjuvant treatment for breast cancer. Lancet 2005, 365 (9453): 60-62.