Study: Tamoxifen Lowers Risk, But New Tumor May Be More Aggressive

Women who take tamoxifen may lower their overall risk of a tumor recurring, but any new cancer is more likely to be of an aggressive type, according to researchers at the Fred Hutchinson Cancer Research Center in Seattle.

The study, according to a report in the Journal of the National Cancer Institute, consisted of almost 9,000 women with breast cancer, with half of them taking tamoxifen as a follow up to their primary treatment and the other half not taking the drug.

Researchers found that 89 of the women taking tamoxifen developed cancer in the previously unaffected breast after 8 years -- 11 percent fewer than the 100 women not taking the drug who developed such tumors.

But when the women not taking tamoxifen developed second tumors, only 4 percent developed the more aggressive estrogen-negative type, whereas the tamoxifen users had a 27 percent incidence of second tumors that were estrogen-negative.

Tamoxifen and other drugs work against tumors sensitive to estrogen, but there are no drugs that target estrogen-negative tumors, said Dr. Christopher Li of the Hutchinson Center.

Li suggests that clinical practices in regard to the use of tamoxifen should not change based on this report, as the results need to be verified by further studies.

Other sources: Journal of the National Cancer Institute, AP