Reducing Breast Cancer Risk Lowers Bone Density

Breast cancer drug Aromasin accelerates bone mineral density loss

(RxWiki News) Women who are at high risk of developing breast cancer are sometimes prescribed medications that block estrogen, the hormone that drives the most breast malignancies. One such drug is Aromasin (exemestane), which new studies show lowers more than cancer risks.

Postmenopausal women who are taking Aromasin to prevent breast cancer are also seeing dramatic increases in the onset of osteoporosis. And even calcium and vitamin D supplements aren't offering much protection against this decline in bone health.

"Know the risks - as well as the benefits - of all medications you're taking."

The research was carried out by researchers with the University Health Network (UHN) and used data from a substudy of the MAP.3 trial studying the effectiveness of Aromasin (exemestane) in preventing breast cancer.

Lianne Tile, M.D., M.Ed., one of the authors of the study, medical director of the Osteoporosis Clinic and staff general internist at University Health Network, said of this first-ever study, "“We found that exemestane worsens age-related bone loss by about three-fold, even in women who take adequate calcium and vitamin D."

For this research, 351 postmenopausal women with an average age of 61 were monitored for two years after started the drug. The participants showed no signs of osteoporosis, were not taking bone medications, but were supplementing with 1200-1500mg calcium and 800IU vitamin D daily.

The women had T-scores (a measure of bone density) of above -2.0 which is considered healthy bone mass for adults. A score of -2.5 indicates osteoporosis, which weakens the bones, making them more vulnerable to fractures.

Following bone mineral density testing (BMD), researchers found the following:

  • A 6.1 percent loss in BMD at the wrist, a common place for breaks, in the treated women compared to a 1.8 percent loss in women not taking the drug
  • A -5 percent change in BMD in the medication group and a 1.3 percent loss in the untreated group
  • Using advanced imaging, women taking Aromasin lost 7.9 percent thickness in cortical bone, which makes up the 80 percent of the human skeleton, vs. a 1.1 percent loss in women who weren't on the drug.

"Our findings suggest that we need to weigh the individual risks and benefits when considering exemestane for the primary prevention of breast cancer. For women taking this medication, it is a good idea to have regular bone monitoring, and adequate calcium and vitamin D,” Dr. Tile concluded.

dailyRx asked Contributing Expert, Adam Brufsky, M.D., Ph.D., about this study. "We knew about the risk of bone loss with exemestane in other prior trials in breast cancer," said Dr. Brufsky, who is professor of medicine at the University of Pittsburgh School of Medicine.

"A bisphosphonate such as alendronate [Fosamax] will counter these side effects, and may prevent breast cancer as well. In the future, we may consider a cocktail of alendronate and exemestane for breast cancer prevention, although we will likely need clinical trials to confirm this," Dr. Brufsky said.

An article on this research was published Online First February 7, 2012 in The Lancet Oncology.

This study was funded by the Canadian Breast Cancer Research Alliance, the Canadian Cancer Society, Canadian Institutes of Health and Pfizer, Inc., the manufacturer of Aromasin.

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Review Date: 
February 8, 2012