Updated from 3:10 p.m. EDTCHICAGO -- Dendreon's ( DNDN) cancer drug Provenge extended the survival of patients with advanced prostate cancer patients by more than four months, according to results from a closely watched clinical trial being presented this afternoon at a medical meeting here. Provenge could become the first so-called cancer immunotherapy or cancer "vaccine" approved for use in the U.S. Dendreon plans to re-file Provenge with the U.S. Food and Drug Administration in the fourth quarter. The agency refused to approve Provenge in 2007. Provenge is not a cure for advanced prostate cancer but the 4.1-month survival benefit nearly matches the result reported in a previous clinical trial of Provenge and exceeds the survival advantage provided by Taxotere, a chemotherapy drug marketed by Sanofi Aventis ( SNY). Dr. David Penson, an investigator in the Provenge study from the University of Southern California, will be discussing detailed results from the phase III study of Provenge later this afternoon at the annual meeting of the American Urological Association. A media embargo on some of the data was lifted prior to the presentation at 3:20 pm EDT. Dendreon shares have more than tripled since the company announced on April 14 that the Provenge study, known as IMPACT, was a success. The stock was up as much as 19% Tuesday before falling 45% to $11.81 right before trading was halted in advance of the Provenge data release. The IMPACT study enrolled 512 men with advanced prostate cancer who no longer responded to hormone therapy. The primary endpoint of the study was to determine whether treatment with Provenge prolonged overall survival of patients compared to a placebo.