Breast cancer preventative reported to weaken bones
A common fear among women is to be stricken with breast cancer. A drug that would reduce or eliminate that risk sounds very appealing. However, a product that sounds too good to be true may be just that. Exemestane (Aromasin) is a new drug that researchers hoped might provide a safe way to prevent breast cancer; however, a new study has reported that the medication is associated with a risk for significant bone loss.
A research team led by Angela M Cheung MD published their findings February 6 online in the British medical Journal The Lancet.
Exemestane is currently used to prevent breast cancer; however, a large study published last June reported that its could reduce the risk of being stricken with breast cancer in the first place by about 65%, compared to a placebo, in women at increased risk of the disease. Two other drugs that can reduce the risk of breast cancer recurrence, tamoxifen and raloxifene, are approved by the Food and Drug Administration (FDA) to prevent breast cancer; however, they have not been used as a preventative; this restriction is in part due to serious side effects such as blood clots. Exemestane is not associated with the side effects associated with those two medications; thus, researchers set out to prove that the drug might be a safe cancer preventative for millions of women at increased risk for breast cancer (i.e., those with a strong family history of the disease).
“One might not be too reassured about the use of exemestane in the prevention setting,” Jane A. Cauley, DrPH, an epidemiologist at the University of Pittsburgh, wrote in a commentary, which accompanied the study. Dr. Cheung, who directs the osteoporosis program at University Health Network in Toronto, countered that the findings should not deter high-risk women from taking the medication. She said, “Sometimes the options are, ‘should I take my breasts out, or should I take a medication such as this?’”
The new study was actually a more detailed evaluation of bone quality in 351 of the 4,560 postmenopausal women who participated in the study published last June. Postmenopausal women received either exemestane or a placebo daily. The women were evaluated by a relatively new technique known as high-resolution peripheral quantitative CT. After about two years, the researchers found that the women who received exemestane had an average 6.1% decrease in the bone mineral density in their distal radius (the lower end of that arm bone near their wrist), compared with a 1.8% decrease in women who received the placebo. The women who received exemestane also had more evidence of a weakening of bone structure as visualized by the advanced CT procedure. The researchers noted that this finding suggested that conventional bone density tests may not be able to detect all the damage caused by the drug.
The lead author of the original study, Dr. Paul E. Goss (director of breast cancer research at Massachusetts General Hospital), noted that the changes in bone structure imaged by the advanced CT procedure had not been proven to increase the fracture risk. He added that in the original study, the women who received exemestane did not experience more fractures than the control group. In addition, he explained that women could take osteoporosis drugs to counter the bone-weakening effect of exemestane.
At present, exemestane is not approved by the FDA for breast cancer prevention; in addition, it is associated with other side effects such as joint pain. Other options are available for women at high risk of breast cancer. An increasing number of these women are undergoing removal of their breasts followed by cosmetic reconstruction.
Reference: The Lancet