Could one pill help prevent breast cancer and build stronger bones at the same time?

It’s possible, say researchers including Silvana Martino, DO, of the Cancer Institute Medical Group in Santa Monica, Calif.

The pill in question is Evista (search), an osteoporosis drug (search). It’s made by Eli Lilly and Company, a WebMD sponsor.

Martino and colleagues pitted Evista against a placebo in a study of more than 4,000 postmenopausal women with osteoporosis. The women had already taken Evista or a placebo in a similar trial for four years. Encouraged by those results, the scientists decided to continue for four more years.

Participants were allowed to stay in the study if they wished. More than 2,700 took 60 mg of Evista daily. The rest took a placebo.

The women were free to take bone-builders like bisphosphonates, calcitonin, or fluoride. They also got daily calcium and vitamin D supplements.

The results were promising.

Women taking Evista had 59 percent fewer cases of invasive breast cancer than the placebo group. They also had 66 percent fewer cases of estrogen-sensitive invasive breast cancer. Overall, breast cancer was 58 percent less common in the Evista group, taking both four-year trials into account.

The side effects weren’t surprising. Evista can cause blood clots. In the study, the Evista takers were about twice as likely to have clotting incidents.

Earlier this month, British researchers reported that Evista had a cancer-protecting effect in a study of postmenopausal women with osteoporosis regardless of whether the women had taken hormone replacement therapy.

Still, questions remain.

No one knows if Evista prevents breast cancer in premenopausal women or those without osteoporosis.

It’s also unclear if the breast cancer drug tamoxifen works better to prevent breast cancer, say experts including Powel Brown, MD, PhD, of Baylor College of Medicine’s Breast Center.

Current studies may clarify Evista’s role in preventing breast cancer, say Brown and colleagues in a journal editorial.

Meanwhile, Evista is only approved for preventing and treating osteoporosis.

By Miranda Hitti, reviewed by Charlotte E. Grayson, MD

SOURCES: Martino, S. Journal of the National Cancer Institute, Dec. 1, 2004; vol 96: pp 1751-1761. Kalidas, M. Journal of the National Cancer Institute, Dec. 1, 2004; vol 96: pp 1731-1733. WebMD Medical Reference from Healthwise: “Pulmonary Embolism: Topic Overview.” WebMD Medical News: “Osteoporosis Drug May Prevent Breast Cancer.” News release, Journal of the National Cancer Institute.