Approval of prostate vaccine urged
Cancer treatment most effective yet in advanced cases, scientists say
A controversial prostate cancer vaccine that previously had been rejected by the Food and Drug Administration improves survival of patients with the advanced form of the disease more than existing treatments and should be brought to market, researchers said Tuesday.
The therapeutic vaccine, called Provenge, extended average survival by four months compared with a placebo, nearly twice as long as the best available chemotherapy, and increased three-year survival by 38 percent, researchers said at a Chicago meeting of the American Urological Association.
“This is going to change the way we treat … metastatic prostate cancer,” said Dr. David Penson, a urologist at the University of Southern California’s Norris Comprehensive Cancer Center. “Any patient who has this form of cancer, this is the drug they are going to want, and it is going to be first-line therapy.”
Added Dr. Stan Gerson, director of the University Hospitals Ireland Cancer Center in Cleveland: “This will be much easier for patients than going through chemotherapy because there are no side effects.”
Penson and Gerson participated in the study, but neither has financial links to Dendreon Corp. of Seattle, which developed Provenge. The foundation provided support for some of the initial research on the vaccine.
As a therapeutic vaccine, Provenge is designed to treat the disease rather than prevent it. Physicians collect specialized immune cells called dendritic cells from the patient’s blood, mix them with proteins collected from the surface of tumor cells and inject them back into the patient in three doses at two-week intervals.
In a study released in 2007, Dendreon found that the vaccine increased survival in patients with metastatic disease by 18 weeks compared with patients given a placebo. After three years, 34 percent of those in the vaccine group survived, compared with 11 percent of those in the placebo group.
An FDA advisory committee recommended that the vaccine be approved for marketing, but the agency disagreed, arguing that the study did not provide evidence that the vaccine slowed progression of tumors.
The decisions provoked outrage among cancer patients.
The new double-blind study involved 512 patients with advanced prostate cancer. Two-thirds received Provenge while the rest received a placebo. Dr. Paul Schellhammer of Eastern Virginia Medical School in Norfolk, Va., said that median survival in the Provenge group was 26 months, compared with 22 months in the placebo group.
That may seem like a short time, experts said, but drugs that provide shorter survival are routinely approved.
“The ability to boost survival for patients is the gold standard endpoint in prostate cancer clinical trials,” said Dr. Ira D. Sharlip, a urologist at the University of California, San Francisco, and a spokesman for the urology association.
The current treatment for such patients is Taxotere, a drug that extends survival two to three months at most and has side effects that include bone and muscle pain, severe allergic reactions, decreases in white and red blood cells, and neuropathy.
But with Provenge, “they might have a little fever, and the next day they are out playing golf,” Penson said.
Dendreon officials said they would reapply to the FDA later this year. They have not said how much the therapy might cost.