Study shows tamoxifen can prevent cancer for years

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TweetStudy shows tamoxifen can prevent cancer for years By Susan Heavey
Tue Nov 15, 4:39 PM ET



WASHINGTON (Reuters) - 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.

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Researchers found that women who took tamoxifen, sold as a generic and by AstraZeneca Plc under the brand Nolvadex, for up to five years were about 43 percent less likely to get breast cancer than those who took a placebo.

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 assigned to 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 Inc. and Roche's Herceptin and others, only tamoxifen has U.S.-approval to prevent it in high-risk women.

Researchers at the National Surgical Adjuvant Breast and Bowel Project network studied women at least 60 years old or who were between ages 35 and 59 with a high risk, such as having an 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, they 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.

Some women took the drug for up to five years, others for less time before researchers told participants in 1998 if they were taking tamoxifen and allowed them to opt for the drug. At that time, findings showed it could reduce cancer risk by 49 percent, and researchers have continued to follow the patients.

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

They also found women taking tamoxifen experienced fewer broken bones than those taking 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 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 percent lower and uterine cancer was about 29 percent 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 and Co.. Those results are due next spring.

European researchers are also studying AstraZenaca's new breast cancer treatment Arimidex, or anastrazole, for prevention.

Like tamoxifen, both drugs also work by blocking the hormone estrogen.

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