A warning is being recommended for certain women who take the drug tamoxifen to treat breast cancer.
A federal health advisory panel says post-menopausal women face a greater risk of the cancer recurring if they carry a variant of a certain gene.
The panel wants tamoxifen's label changed to add that warning.
But they're leaving it to the Food and Drug Administration to decide if the label should also urge genetic testing for women who've gone through menopause, before they take tamoxifen.
The drug has been on the market for nearly 30 years, and is used to both treat breast cancer and to prevent the disease in women who may be at risk.