Long-lasting Breast Cancer Fighter

By Lucy Williams, Ivanhoe Health Correspondent

ORLANDO, Fla. (Ivanhoe Newswire) -- The breast cancer-fighting benefits of tamoxifen last well beyond the time patients spend taking the drug, according to two recent studies. The risk-reducing effects of the drug last at least 10 years after treatment, even after side effects desist.

Tamoxifen is an anti-estrogen drug prescribed to women at high risk for breast cancer. The drug fights estrogen receptor (ER)-positive breast cancer by blocking estrogen from breast cancer cells, which slows or stops the growth of dangerous cells in the body.

"For the right population, the benefit is significant. If you have a 55-year-old with three family members with breast cancer, she is someone who would significantly benefit from tamoxifen," Nikita Shah, M.D., of M.D. Anderson Cancer Center in Orlando, Fla., told Ivanhoe.

For the International Breast Cancer Intervention Study, 7,145 women at risk for breast cancer took either 20 milligrams of tamoxifen or a placebo each day for five years. Four years into the trial, researchers found participants taking tamoxifen were 32-percent less likely to have developed ER-positive breast cancer. ER-negative breast cancer rates were similar in both groups.

Eight years after initial enrollment, participants who took tamoxifen were 27-percent less likely to have developed ER-positive breast cancer. Although breast cancer rates were similar to the earlier analysis, tamoxifen side effects decreased after patients stopped taking the drug.

General side effects of tamoxifen are similar to menopause symptoms. Some women experience hot flashes, irregular menstrual periods, headaches, fatigue and nausea. Serious side effects can include deep-vein thrombosis and pulmonary embolism.

"Studies have suggested the benefit of tamoxifen is typically so much greater than the potential side effects," Dr. Shah said.

In another study, researchers at the Royal Marsden Hospital in London analyzed 13 years of data from 2,471 women randomly assigned to take 20 milligrams of tamoxifen or a placebo each day for eight years. After six years, there was no difference in breast cancer rates between the two groups.

Twenty years after the initial study, researchers found tamoxifen reduced the risk of ER-positive breast cancer by 39 percent. This reduction occurred mostly at the end of the follow-up period.

In both studies, tamoxifen only reduced the risk for ER-positive cancers. Further research is necessary to identify ER-positive breast cancer risk so doctors can prescribe the drugs to candidates who will benefit the most.

"There's no predicting whether someone is at-risk for an ER-positive or an ER-negative tumor," she said. "A drug like tamoxifen would be recommended for all women who are considered at high risk for breast cancer."

This article was reported by Ivanhoe.com, which offers Medical Alerts by e-mail every day of the week. To subscribe, click on: http://www.ivanhoe.com/newsalert/.

SOURCE: Ivanhoe interview with Nikita Shah, M.D.; Journal of the National Cancer Institute, 2007;99:272-282