An FDA advisory panel on Wednesday recommended that a warning label be added to tamoxifen, an agency-approved drug for treating and preventing breast cancer, the AP/Seattle Post-Intelligencer reports (Bridges, AP/Seattle Post-Intelligencer, 10/18).

FDA in 1998 approved tamoxifen to reduce breast cancer risk after a study showed it decreased the likelihood of women developing the disease by 50%.

The drug - which can have side effects including uterine cancer in women who have not had hysterectomies and blood clots - was sold under the brand name Nolvadex by AstraZeneca and is now marketed by several generic drugmakers.

Under current treatment guidelines, physicians are advised to consider tamoxifen for women whose breast cancer risk is 1.67% or higher.

Risk is assessed using a test that accounts for age, family history, childbirth and other factors (Kaiser Daily Women’s Health Policy Report, 7/24).

The panel - citing recent studies that found the drug does not work well in the 7% to 10% of women diagnosed with breast cancer who carry a variant of the gene CYP2D6, which affects how their bodies process the drug - recommended the agency change the drug’s label to include a warning that postmenopausal women might be at higher risk of breast cancer recurrence if they take tamoxifen, the AP/Post-Intelligencer reports (AP/Post-Intelligencer, 10/18).

“The risk signal needs to be indicated very clearly to patients,” Howard McLeod, a panel member and a director at University of North Carolina’s Institute for Pharmacogenomics and Individualized Therapy, said, adding, “Patients may choose to continue with tamoxifen for other reasons, but at least they need to be informed of the risk that is present.”

Matthew Goetz, assistant professor of oncology at the Mayo Clinic College of Medicine, said it is important to study the efficacy of tamoxifen because there are other treatments available to postmenopausal women that could be more beneficial.

He added, “Tamoxifen is not the only kid on the block anymore” (Kowsmann, Dow Jones/MarketWatch, 10/18).

According to Lawrence Lesko, FDA pharmacology chief, the label changes could take up to six months to take effect (AP/Post-Intelligencer, 10/18).