Study shows tamoxifen can prevent cancer for years

Women at high risk for breast cancer who take the well-known drug tamoxifen can reduce their long-term risk of developing the disease, according to a new study released on Tuesday. Researchers found that women who took tamoxifen for up to five years were about 43% less likely to get breast cancer than those who took a placebo. Tamoxifen is sold in the United States as a generic drug as well as under the brand name Nolvadex by AstraZeneca.

Out of 6,681 women taking the drug, 145 have developed cancer since the study began in 1992, compared with 250 cases in 6,707 women who took a placebo, according to scientists at the Pittsburgh-based research network that conducted the trial with funding from the National Cancer Institute.

"This final analysis confirms that tamoxifen reduces the risk of invasive breast cancer in both pre- and post-menopausal women at increased risk for the disease," they said in a statement.

While a number of new medicines have been shown to treat the disease, such as Genentech and Roche's Herceptin and others, only tamoxifen has U.S. approval to be prescribed for high-risk women.

Researchers at the National Surgical Adjuvant Breast and Bowel Project network studied women at least 60 years of age or who were between ages 35 and 59 and at high risk for developing breast cancer, such as having a mother or sister who had been diagnosed or experiencing breast lumps that were then tested. About 17 out of every 1,000 women who are over 60 may develop the disease within five years, researchers said. Breast cancer is one of the leading cancers among U.S. women. More than 200,000 are diagnosed, and another roughly 40,000 die from it each year, according to the American Cancer Society. Studies have shown that lesbians are at a higher risk of breast cancer than their heterosexual peers.

Some women took the drug for up to five years, others for less time. In 1998 researchers allowed all participants in the study to opt for the drug. At the time findings showed that tamoxifen could reduce breast cancer incidence by 49% among women at high risk for the disease. Researchers have since continued to track the study participants.

"There is proof of a benefit from tamoxifen beyond the time a woman is taking the pills," said Leslie Ford, coauthor of the study and associate director for NCI's Division of Cancer Prevention.

They also found that women taking tamoxifen experienced fewer broken bones than those taking a placebo. Eighty women on the drug reported a hip, wrist, or spine fracture compared with 116 reports from those on the placebo.

The earlier results also found that tamoxifen increased the risk of cancer in the uterus lining as well as blood clots in the lungs and major veins. These new findings showed no statistically significant change, researchers said, although the rate of lung blood clots was 11% lower and uterine cancer was about 29% higher than in 1998.

Other possible side effects, including stroke and cataracts, remained about the same as long as patients did not take the drug longer than five years, which could increase possible problems, researchers said.

The group is also studying tamoxifen's ability to prevent the disease in comparison to raloxifene, an osteoporosis drug sold under the brand Evista by Eli Lilly. Those results are due next spring.

European researchers are also studying AstraZenaca's new breast cancer treatment Arimidex, or anastrozole, for prevention. Like tamoxifen, both drugs also work by blocking the hormone estrogen. (Reuters, with additional reporting by Advocate.com)