A danger emerges in long-term tamoxifen use

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Some breast cancer patients take the drug tamoxifen to reduce the risk of developing a second breast cancer. However, a study published today makes an important distinction in this strategy. Tamoxifen, it appears, cuts the risk of the more common type of cancer that is less aggressive but actually increases the risk of a rarer type of breast cancer that is aggressive and harder to treat.

The study, published in Cancer Research, compared breast-cancer patients who received tamoxifen for at least one year with those who did not take the drug. The researchers, from the Fred Hutchinson Cancer Research Center in Seattle, found that the drug was associated with a 60% reduction in the risk of developing a second estrogen receptor-positive breast cancer. But tamoxifen appeared to increase the risk of developing an estrogen receptor-negative breast cancer by 440% -- a more than fourfold increase.

However this finding should not discourage women from taking tamoxifen to prevent a second cancer, said the lead author of the study, Dr. Christopher Li.

‘It is clear that estrogen-blocking drugs like tamoxifen have important clinical benefits and have led to major improvements in breast cancer survival rates,’ Li said in a news release. ‘However, these therapies have risks, and an increased risk of ER-negative second cancer may be one of them. Still, the benefits of the therapy are well established and doctors should continue to recommend hormonal therapy for breast cancer patients who can benefit from it.’

-- Shari Roan