Post-menopausal women who take tamoxifen to treat breast cancer face a greater risk of recurrence if they have a specific genetic variation, federal health advisers said Wednesday in recommending that a warning be added to the drug’s label.
Recent studies have found tamoxifen does not work as well in women with breast cancer who carry a variant of a gene called CYP2D6. An estimated 7 percent to 10 percent of women with breast cancer may have that special form of the gene, which affects how their bodies process the drug.
A panel of Food and Drug Administration advisers recommended the agency change tamoxifen’s label to warn post-menopausal women of that potential risk.
“The bottom line is, the consensus was that the information is important enough to be included in the label,” said FDA pharmacology chief Dr. Lawrence Lesko.
However, the clinical pharmacology panel left it to the FDA to decide whether the drug’s label should recommend genetic testing of post-menopausal breast cancer patients before they are prescribed tamoxifen. Still, the FDA will consider adding such language perhaps in the form of a suggestion to the label, Lesko said.
The FDA first approved tamoxifen in 1977. It is made in generic form by multiple drug companies.
The drug is now use to both treat breast cancer and to prevent the disease in women who may be predisposed to it. The drug blocks estrogen, a hormone that stimulates the growth of most tumors after menopause.
Lesko said the label changes could take six months to put in place. Since 2003, the FDA has taken three other drugs before the panel to discuss adding genetic-specific information to their labels. They include the blood-thinner warfarin; updates to its label are forthcoming, Lesko said.
The FDA isn’t required to follow the advice of its outside panels, but usually does.