Some breast-cancer patients take the drug tamoxifen to cut the risk of a second breast cancer. But a study published Tuesday makes an important distinction. Tamoxifen, it appears, cuts the risk of the more common type of cancer that is less aggressive but 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 percent 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 percent.
This study should not discourage women from taking tamoxifen, said the lead author, 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.”
