Tamoxifen reduces long-term risk of cancer

Nov 16 2005

According to a new study released this week, women at high risk for breast cancer who take the well-known drug Tamoxifen, can reduce their long-term risk of developing the disease.

Researchers found that women who took Tamoxifen, for up to five years were about 43 percent less likely to get breast cancer than those who took a placebo.

According to the researchers that conducted the trial, 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.

The researchers say that 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.

Although a number of new medicines have been shown to treat the disease, such as 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.

They said approximately 17 out of every 1,000 women who are over 60 may develop the disease within five years.

According to the American Cancer Society, breast cancer is one of the leading cancers among U.S. women; more than 200,000 are diagnosed and around 40,000 die from it each year.

In the study 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, their findings demonstrated it could reduce cancer risk by 49 percent; the researchers have continued to monitor the patients.

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 had also suggested that Tamoxifen increased the risk of cancer in the uterus lining as well as blood clots in the lungs and major veins, but the new findings showed no statistically significant change, say the researchers, 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. Those results are due next spring.

European researchers are also studying AstraZenaca's new breast cancer treatment Arimidex, or anastrazole, like Tamoxifen, both drugs work by blocking the hormone estrogen.