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.
The drug was found to be more effective than Tamoxifen and has fewer side-effects.
IBIS-II was conducted by the Australia and New Zealand Breast Cancer Trials Group (ANZBCTG), with 818 women from Australia and New Zealand participating 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.
“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,” the Co-Chair of IBIS-II and Director of Research for the ANZBCTG, Professor John Forbes AM, said
“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:
“This landmark study shows that Anastrozole could be valuable in helping to prevent breast cancer in women at higher than average risk of disease,” Professor Forbes said: “We now need accurate tests that will predict which women will most benefit from Anastrozole.”
In the case of Newcastle’s Alison Peterson, a participant in IBISII, the threat of cancer has been omnipresent and terrifyingly real.
Her three sisters have all endured a brush with breast cancer – one lost her battle.
“Tracey was diagnosed at 35 and died at 40, around 14 years ago,” Alison explains. “My oldest sister Gail has had both breasts removed in past five years and had complications, and my other sister Donna had one lump removed and has undergone chemotherapy.”
Alison had a lump removed 12 years ago, which was benign, but otherwise has remained healthy.
“I’m not doing it for me; I’m doing it for other people because I saw what Tracey went through,” she adds. “Professor Forbes and his team are absolutely amazing … I’ve never really worried about being next because I feel safe.”
* John Forbes is Professor of Surgical Oncology at the University of Newcastle and Director of Surgical Oncology at the Calvary Mater Newcastle Hospital. He researches in collaboration with HMRI’S Cancer Research Program and the Hunter Cancer Research Alliance.