Breast Cancer Drug May Increase Bone Loss

A drug that can cut the risk for breast cancer has a serious down side: Aromasin appears to cause bone loss in postmenopausal women.

Researchers at the University Health Network in Toronto, Canada, looked at more than 4,500 women who were in a trial that compared Aromasin (exemestane) with a placebo. The drug cut the risk for breast cancer by 65 percent.

Bone loss

They found that after two years of taking the drug, though, women had an 8 percent loss of bone, compared with just 1 percent in women who were in the placebo group. The area of bone affected was the cortical bone, or the outer shell of bone that provides most of the support. This area of bone loss plays a role in about 80 percent of fractures in older adults.

"The drug did affect bone density at the hip and spine," says lead researcher Angela Cheung, M.D. But, she adds, "it does not affect everyone."

Exemestane is an aromatase inhibitor and works by suppressing the female hormone estrogen. Aromatase inhibitors are standard treatment for postmenopausal women who have estrogen-positive breast cancer in its early stages.

Other researchers had speculated that exemestane might cause less bone loss than similar drugs and might even stimulate bone formation.

Still effective

Dr. Cheung says that the fear of bone loss shouldn't be a reason not to take the drug, because it is so effective at reducing the chances for breast cancer.

Stephanie Bernik, M.D., at Lenox Hill Hospital in New York City, agrees. The benefit of the drug outweighs that risk for most women, she says.

But if there is a family history of osteoporosis, it may not be the best choice, Dr. Bernik says.

Dietary supplements

Women taking this drug should also be taking calcium and vitamin D supplements, and having their bone density monitored, Dr. Cheung says.

"You really need to pay attention to your bone health when you take this medication, especially for preventing breast cancer," she says.

The study was published in the online edition of Lancet Oncology.

Always talk with your health care provider to find out more information.