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Weekly dose of osteoporosis drug prevents bone loss after breast cancer treatment

September 19, 2007

Breast cancer survivors who took a weekly dose of risedronate, sold as Actonel, lost significantly less bone than those who did not take the drug, according to a two-year study from the University of Pittsburgh School of Medicine presented this week at the 29th annual meeting of the American Society for Bone and Mineral Research. Scientific sessions continue through Wednesday at the Hawaii Convention Center.

Susan Greenspan, M.D., director of the Osteoporosis Prevention and Treatment Center and Bone Health program at the University of Pittsburgh Medical Center, and colleagues evaluated 87 women, mean age 50, enrolled in the Prevention of Osteoporosis in Postmenopausal Women with Breast Cancer Following Chemotherapy study. All participants in the randomized, double-blind trial received calcium and vitamin D supplements. However, half took 35 milligrams of risedronate once a week while others took a placebo.

"Chemotherapy drugs and other medical treatments for breast cancer are known to induce menopause, which can kick-start bone loss, putting survivors at risk for osteoporotic fractures," said Dr. Greenspan, an internationally respected osteoporosis researcher and professor of medicine at Pitt. "This study also looked at changes in spine and hip bone mineral density, as well as evidence of bone breakdown."

Ninety-seven percent of study participants had normal or low bone mass at enrollment. At baseline, many were taking tamoxifen, a breast cancer drug aimed at estrogen-sensitive tumors that also is sometimes used as a preventive therapy by women at high risk for breast cancer.

While tamoxifen can have a positive impact on bone in postmenopausal women, a small percentage of women were taking aromatase inhibitors (also used for prevention), which can have a negative effect on bone. During the second year of the study, about half the women began taking aromatase inhibitors and stopped taking tamoxifen.

"After 24 months, women in the placebo group had significant bone loss in the spine and hip that we didn't see in women taking risedronate," noted Dr. Greenspan. "In fact, women taking risedronate had a bone density much higher in the spine and hip than women in the placebo group." The researchers also observed that the greatest bone loss was found in women on aromatase inhibitors. Even so, risedronate continued to be successful in preventing bone loss.

"We conclude that once weekly doses of risedronate improves bone density and prevents excess bone loss in breast cancer survivors," the researchers noted.

University of Pittsburgh Schools of the Health Sciences