DRUG CUTS BREAST CANCER CASES BY OVER 50%

Taking the breast cancer drug anastrozole for five years reduced the chances of postmenopausal women at high risk of breast cancer developing the disease by 53 per cent compared with women who took a placebo, according to a study published in The Lancet* today.

The results of the international prevention clinical trial called IBIS-II, could offer a new option for preventing breast cancer in moderate to high risk postmenopausal women which is more effective than tamoxifen and has fewer side-effects. IBIS-II was conducted locally by the Australia and New Zealand Breast Cancer Trials Group (ANZBCTG) and 818 women from Australia and New Zealand participated in the study across 30 institutions.

IBIS-II involved almost 4,000 postmenopausal women worldwide at high risk of breast cancer with half being given 1mg of anastrozole daily and half given a placebo. In the five years of follow up 40 women in the anastrozole group developed breast cancer compared to 85 women in the placebo group.

Professor John Forbes AM, the International Study Co-Chair of IBIS-II and Director of Research for the ANZBCTG, said: “This research is a very important development in breast cancer prevention. We now know anastrozole should be the drug of choice when it comes to reducing the risk of breast cancer in postmenopausal women with a family history or other risk factors for the disease. This class of drugs is more effective than current drugs such as tamoxifen and crucially, it has fewer side effects.”

“Unpleasant side effects such as acute aches and pains have often been associated with oestrogen depriving drugs. However, in this study, the reported side effects were only slightly higher than in the placebo arm. This means most symptoms were not drug related, and the concern about side effects for this type of drug may have been overstated in the past.

“This very positive result provides women at high risk of breast cancer new options to manage their risk. We know prevention is a key concern for women and we sincerely thank the women of Australia and New Zealand who participated in IBIS-II for their contribution to this new knowledge.”

Many breast cancers are fuelled by the hormone oestrogen. Anastrozole works by preventing the body from making oestrogen and has for many years been used to treat postmenopausal women with oestrogen receptor positive breast cancer.

Women were judged to be at high risk of breast cancer if they fulfilled one of the following criteria: having two or more blood relatives with breast cancer, having a mother or sister who developed breast cancer before the age of 50, having a mother or sister who had breast cancer in both breasts, or having certain high risk types of benign breast disease.

Professor Forbes said: “This landmark study shows that anastrozole could be valuable in helping to prevent breast cancer in women at higher than average risk of disease. We now need accurate tests that will predict which women will most benefit from anastrozole.”

The ANZBCTG is Australia’s national organisation dedicated entirely to breast cancer research. It conducts a national clinical trials research program for the treatment, prevention and cure of breast cancer. The research program involves multicentre clinical trials and collaboration with more than 80 institutions and over 600 researchers throughout Australia and New Zealand. More than 14,000 women have participated in ANZBCTG breast cancer clinical trials. The ANZBCTG’s fundraising department is the Breast Cancer Institute of Australia (BCIA).

Professor Forbes is Professor of Surgical Oncology at the University of Newcastle and is Director of Surgical Oncology at the Calvary Mater Newcastle Hospital. IBIS-II received funding in Australia from the National Health and Medical Research Council.

Notes to editor: *Cuzick, J.et al Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double blind, randomised placebo-controlled trial (2013) The Lancet. The full paper can be downloaded here: http://press.thelancet.com/IBISII.pdf

About IBIS-II (International Breast cancer Intervention Study II)

• IBIS-II is being coordinated in Australia and New Zealand by the Australia and New Zealand Breast Cancer Trials Group and globally by Cancer Research UK. The trial is taking place in 21 countries including Australia, New Zealand, India, Chile, Germany, Italy and the United Kingdom.
• 3,864 women participated in IBIS-II worldwide, with 1,920 assigned to anastrozole and 1,944 assigned to placebo.
• 818 women from Australia and New Zealand participated in IBIS-II from 30 institutions.
• IBIS-II was supported in Australia by the National Health and Medical Research Council.