FDA advisers endorse experimental prostate cancer vaccine

Federal health advisers have endorsed an experimental vaccine to treat advanced prostate cancer as safe and effective.

The Food and Drug Administration advisers voted unanimously Thursday to say Provenge is safe. They then voted 13-4 to say there is substantial evidence that it works in treating advanced prostate cancer that no longer responds to hormone treatment.

The FDA isn't required to follow the advice of its advisory committees, but it usually does. A final FDA decision on whether to approve Provenge, also called sipuleucel-T, is expected May 15. The vaccine is made by Seattle-based Dendreon Corp.

If approved, Provenge would become the third cancer vaccine but the first that is therapeutic. FDA-approved vaccines against liver and cervical cancer are both preventive.

Neither of two studies Dendreon submitted to the FDA in support of its application achieved their primary goal in showing Provenge delayed the progress of the disease, according to the agency.

However, the results of the first study suggested the vaccine could extend the lives of patients by 4.5 months compared to those given only dummy treatment. The only other prostate cancer drug shown to prolong the lives of patients is Taxotere, also called docetaxel.

A larger, ongoing study of Provenge is looking specifically at whether it increases longevity of prostate cancer patients.

If ultimately approved, Provenge would become the first of a new class of therapies designed to stimulate a patient's own immune system against cancer, according to Dendreon.

Prostate cancer is the most common cancer in American men, other than skin cancer. The American Cancer Society estimates there will be about 220,000 new cases this year, and about 27,000 deaths.

The vaccine combines a protein found in most prostate cancers with a substance that helps specialized immune system cells recognize cancer as a threat, just as they recognize and confront germs that enter the body.

The treatment is customized for each patient. Doctors collect these cells from a patient's blood, mix them with the vaccine, and then give the concoction back to the patient.

Dendreon also is testing Provenge for less serious cases of prostate cancer.

The panelists also recommended that an increased risk of stroke in patients receiving the vaccine be monitored.