PROVENGE IMPROVES SURVIVAL

April 29, 2009 (Chicago, Illinois) — Phase 3 results from the Immunotherapy for Prostate AdenoCarcinoma Treatment (IMPACT) study, presented here at the American Urological Association (AUA) 104th Annual Scientific Meeting, showed that prostate cancer immunotherapy with sipuleucel-T (Provenge, Dendreon Corp.) extended median survival by 4.1 months and improved 4-year survival by 38%.

Results from the IMPACT study were presented by David F. Penson, MD, MPH, professor of medicine at the University of Southern California at Los Angeles. The study involved 512 men with minimally or asymptomatic metastatic castrate-resistant prostate cancer who were randomized in a 2:1 fashion to sipuleucel-T or placebo.

The vaccine was manufactured from the patient's leukocytes, which were expanded over a 2- or 3-day period and then reinfused on day 3 or 4 on an outpatient basis. Three cycles were given over the course of a month.

Sipuleucel-T extended median survival by 4.1 months; median survival was 25.8 months with active treatment and 21.7 months with placebo.

Three-year survival was improved by 38% compared with placebo (31.7% vs 23.0%).

"This 4-month extension in survival is very, very significant," Dr. Penson told Medscape Urology. "These patients have a life expectancy of about 2 years, so giving them 4 more months is pretty important. It gives them about 20% more life. And [sipuleucel-T] does it with minimal adverse events. So there is improved survival with good quality of life."

Treatments were extremely well tolerated, with chills reported in 54.1% of patients (vs 12.5% with placebo), fever in 29.3% (vs 13.7%), headache in 16.1% (vs 5%), and flu-like symptoms in 9.8% (vs 4.3% ). Most adverse events lasted only a few days and were treatable with aspirin. "Some of our patients were golfing the day after treatment," Dr. Penson told reporters.

"The IMPACT study achieved a P value of .032, successfully exceeding the prespecified level of statistical significance," according to a Dendreon release.

Last year, the US Food and Drug Administration (FDA) deferred approval of sipuleucel-T until a statistically significant improvement in survival could be shown.

"The company and the FDA have to get back together to re-evaluate the results, but in my opinion, I think they should approve it."

AUA spokesman J. Brantley Thrasher, MD, chair of the Department of Urology at the University of Kansas in Kansas City, Kansas, pointed out to Medscape Urology that "last year, the FDA put a damper on the approval process. They were looking for more survival data. This should give it to them."

"This will cause a big splash," Dr. Thrasher continued. "We don't have anything for patients with hormone-refractory disease, which is very aggressive. . . . Improved survival with T cell immunotherapy is really very significant."