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Tamoxifen acts as a preventive drug in women with a family history of breast cancer. Users of tamoxifen have a 30 percent lower risk, compared to women who do not use the drug. That is the conclusion of new research conducted at the British Queen Mary University, London. The results have been published in The Lancet Oncology.

Tamoxifen, an antagonist of the estrogen receptor, is used for treating estrogen-receptor positive breast cancer. In the International Breast Cancer Intervention Study (IBIS), British scientists discovered that the drug has a preventive effect as well.

The IBIS study was conducted in more than 7,000 pre and post-menopausal women of 35-70 years old, who all had a family history of breast cancer. They were divided at random to receive either a daily dose of tamoxifen or a placebo for five years. Subsequently, the health of all participants was monitored for a maximum of 22 years. Results showed that after using tamoxifen, 251 women developed breast cancer versus 350 women from the placebo group – a decrease of 29 percent. The number of women with estrogen-receptor positive breast cancer - accounting for two thirds of all breast cancers - was reduced with 35 percent.

In spite of the promising results, Professor Jack Cuzick, leading author of the study, emphasises that the monitoring of the participants has to continue for at least ten years to determine the influence of tamoxifen on death rates. Although not observed in the IBIS study, use of the drug is associated with a higher prevalence of endometrial cancer. Nevertheless, Cuzick thinks the outcomes are promising: “We hope that these results will stimulate the use of preventive medication in women who have a family history of breast cancer.”

Sources: Pharmafile, The Lancet Oncology

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