Eli Lilly and Co’s Evista osteoporosis drug works as well as the older tamoxifen in reducing the risk of breast cancer in high-risk women, with fewer dangerous side effects, researchers said on Monday.

The results of the 19,000-woman Study of Tamoxifen and Raloxifene (STAR) trial show that Evista, known generically as raloxifene, is less likely than tamoxifen to cause blood clots and uterine cancer.

“In STAR, both drugs reduced the risk of developing invasive breast cancer by about 50 percent,” the National Cancer Institute said in a statement.

Tamoxifen, sold as a generic and by AstraZeneca Plc under the brand name Nolvadex, has long been prescribed to treat and prevent breast cancer. Lilly said it would seek U.S. Food and Drug Administration approval to market Evista both for osteoporosis and to prevent breast cancer.

“Today, we can tell you that for postmenopausal women at increased risk of breast cancer, raloxifene is just as effective, without some of the serious side effects known to occur with tamoxifen,” said study chair Dr. Norman Wolmark.

Breast cancer is the second leading cause of cancer death among U.S. women, after lung cancer. More than 200,000 people are diagnosed and another roughly 40,000 die from it each year, according to the American Cancer Society. Globally, 1.2 million women and a few men are diagnosed with breast cancer annually.

The lifetime risk for a woman in the industrialized world is roughly one in nine. But the risk is much higher risk for those with several risk factors including having a mother or sister with the disease, never having had a child, or having had a number of suspicious-looking breast lumps.

RAISING OTHER RISKS

Some women are nervous about taking tamoxifen because it can raise the risk of uterine cancer and blood clots.

Evista does not carry these risks, the five-year STAR trial showed.

“Women who were prospectively and randomly assigned to take raloxifene daily, and who were followed for an average of about four years, had 36 percent fewer uterine cancers and 29 percent fewer blood clots than the women who were assigned to take tamoxifen,” the National Cancer Institute, which helped organize the trial, said.

Both drugs come as pills and both mimic the effects of the hormone estrogen on cells, although in a way that appears to be safer than estrogen itself. Estrogen is linked to most breast cancer cases.

Both drugs also reduce the risk of osteoporosis. The bone-thinning disease becomes much more common after women enter menopause, as do cancer, stroke and heart disease.

STAR was one of the largest breast cancer prevention clinical trials ever conducted, with 19,747 postmenopausal women randomly given a daily dose of Evista or Nolvadex for five years.

“Women taking either drug had equivalent numbers of strokes, heart attacks, and bone fractures,” the NCI said.

Among the 9,745 women in the raloxifene group, 167 developed invasive breast cancer, compared to 163 of 9,726 women in the tamoxifen group.