Can Breast Cancer Be Prevented – Safely?
Until now, women at high risk for breast cancer have been stuck between a rock and a hard place when making a decision on drug therapy for the prevention of breast cancer. Although tamoxifen and raloxifene are approved to prevent breast cancer, the possible side effects - uterine cancer and blood clots - are themselves as life threatening as breast cancer.
Finally there is encouraging news! A major study has now concluded that exemestane (Pfizer Inc.'s brand name Aromasin), a drug currently used to prevent recurrences of breast cancer, can also prevent it from occurring in the first place. It can cut the risk of developing breast cancer by more than half, without the side effects. According to Dr. Paul E. Goss, professor of medicine at Harvard and Massachusetts General Hospital, exemestane is safe and highly effective in preventing breast cancer.
How does exemestane work to prevent breast cancer? Exemestane belongs to a class of compounds called aromatase inhibitors. Aromatase inhibitors stop the production of estrogen in post-menopausal women, blocking the enzyme aromatase, which turns the hormone androgen into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells.
The Trial:
4,560 post-menopausal women in the United States, Canada, France and Spain who were considered to be at a higher than normal risk of developing breast cancer either because of being over 60 or other factors participated.
After a follow-up of about three years, 11 women getting the drug had developed invasive breast cancer compared with 32 of the women receiving a placebo. That is a reduction in risk of 65%.
What are the side effects? Women who took exemestane had more hot flashes and arthritis than those who had the placebo.
Will the cost of exemestane be out of reach for many women? The patent protection on the drug expired in April making it possible for the availability of generic versions and therefore lower prices. The only downside is that Pfizer now has little incentive to seek regulatory approval for the drug for preventing breast cancer.
Will Pfizer seek regulatory approval for exemestane for preventing breast cancer? So far, Pfizer has declined to comment. However, since Pfizer did help to pay for the study, perhaps we can be cautiously optimistic. Stay tuned; we’ll keep you posted.If you are a post-menopausal woman at high risk for developing breast cancer, contact your doctor to discuss whether exemestane is a good option for you.
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