Drug may reduce risk of developing breast cancer in high-risk women

In collaboration with Adfero

A drug called exemestane (brand name Aromasin) significantly reduces the risk of breast cancer in healthy postmenopausal women who are at higher than average risk of developing the disease, according to research presented at a major US conference.

Exemestane is a type of hormone therapy called an aromatase inhibitor and is currently used to treat oestrogen-receptor-positive breast cancer in women who have been through the menopause.

The drug works by blocking the production of oestrogen, which fuels the growth this type of cancer.

According to the latest research, presented at the annual meeting of the American Society of Clinical Oncology and published in the New England Journal of Medicine, exemestane may also be effective at preventing the disease from developing in the first place.

Scientists at Canada's NCIC Clinical Trials Group led a Phase III clinical trial involving the drug, which included 4,560 women in Canada, the US, France and Spain.

All of the participants were postmenopausal and had at least one characteristic associated with an increased risk of developing breast cancer, such as a family history of the disease or early age at first menstrual period.

Half of the women were given exemestane, while the others received a placebo (dummy drug).

After a median of three years, researchers found that women who took exemestane were 65 per cent less likely to have developed invasive breast cancer than those who took the placebo.

There were also fewer pre-cancerous lesions in women who took exemestane.

Side-effects included fatigue, hot flushes, insomnia and joint pain.

Dr Michael Wosnick, vice-president of research at the Canadian Cancer Society, said: "The results are extremely exciting because they have the potential to impact thousands of women.

"The results of this study offer an important new option to prevent this devastating disease in women who are at higher risk for it."

Dr Jean Wactawski-Wende, who co-authored the study at the University of Buffalo, noted that there were few side-effects.

She added: "Exemestane is already being used in thousands of women who already have breast cancer to prevent a recurrence, so we expect it will be generally acceptable for use in women at high risk who want to reduce their chances of developing breast cancer in the first place."

Dr Lesley Walker, Cancer Research UK's director of cancer information, said: "This study adds to growing evidence that aromatase inhibitors could be valuable in helping to prevent breast cancer in women at higher than average risk of disease.

"Our scientists launched the world's first pilot trial of breast cancer prevention at the Royal Marsden Hospital in 1986. It's encouraging to see that this pioneering work is beginning to bear fruit.

"Cancer Research UK is also supporting a breast cancer prevention trial - IBIS-II - with another aromatase inhibitor called anastrozole. Results from this trial, and the longer-term follow up of exemestane, will be important to measure the protective effects and side effects of the aromatase inhibitors."


  • Goss, P. E. et al. Exemestane for Breast-Cancer Prevention in Postmenopausal Women. N Engl J Med 2011. DOI: 10.1056/nejmoa1103507