Dr. Paula Klein, a breast cancer specialist, said she will start prescribing the drug for early-stage patients immediately, but stressed the importance of follow-up data on patient survival.
“This does not yet prove to us that using the antibody in this setting will result in more cures. That is still a hypothesis,” said Klein, who directs the breast cancer program at Continuum Cancer Centers of New York.
The FDA said Monday’s approval was based on a 417-woman study comparing Perjeta in different combinations against older breast cancer treatments. When Perjeta was combined with Herceptin, another Genentech drug, and standard chemotherapy, 39 percent of women saw their cancer reach undetectable levels. Only 21 percent of women experienced the same results from taking Herceptin and chemotherapy alone. After drug treatment all the women received standard breast surgery to remove any cancerous tumors. Genentech says this surgery allowed researchers to confirm the presence or absence of cancer.
Like Herceptin, Perjeta only works in a subset of about 20 percent of breast cancer patients who have tumors that overproduce a protein known as HER-2. This protein causes cancer cells to divide and grow faster than usual.
A spokeswoman for Genentech said a regimen of Perjeta plus Herceptin would cost between $27,000 and $49,000, depending on how long the patient takes the combination. The new Perjeta label will recommend a course of treatment between nine and 18 weeks.
Breast cancer is the second most deadly form of cancer in U.S. women, behind only lung cancer, and is expected to kill more than 39,000 Americans this year, according to the National Cancer Institute. About 6,000 to 8,000 deaths per year are attributed to the HER-2 form of the disease.
Breast cancer is highly treatable when detected early. More than 98 percent of women who are diagnosed with first-stage breast cancer survive at least five years, according to NCI figures.