Prostate cancer vaccine helps patients live longer

Provenge, prostate cancer vaccine made by Seattle-based Dendreon Corp., can help patients with severe, advanced disease live a little bit longer, U.S. researchers reported on Wednesday.

The therapeutic vaccine added a few months to the lives of men with otherwise untreatable prostate cancer, the researchers said. One of several experimental tailored approaches to cancer treatment, Provenge is created by mixing a synthetic version of prostatic acid phosphatase (PAP) with dendritic cells harvested from the study patients. This preparation is designed to break the patient’s immune tolerance to PAP, an antigen found on most prostate cancer cells “A therapy that prolongs life yet avoids the side effects of other therapeutic approaches is clearly attractive to patients and physicians alike,” said Dr. Eric Small, who led the study at the University of California San Francisco School of Medicine. The vaccine helped patients live an average of nearly 4 months, or 18% longer, the researchers told a joint meeting of the American Society of Clinical Oncology, the Prostate Cancer Foundation, the American Society for Therapeutic Radiology and Oncology, and the Society of Urologic Oncology. Dendreon’s vaccine, made with South San Francisco-based Titan Corp., is designed to stimulate the immune system to attack the 95% of prostate cancer cells that generate PAP. A patient’s own immune cells are collected, sensitized to the protein, then reinfused into the patient. Small and colleagues tested this highly tailored therapy on 127 men with prostate cancer that had spread and that no longer responded to hormone therapy.As part of a phase III trial for Food and Drug Administration approval, 82 men received the vaccine while 45 received placebo. On average, the men who got the vaccine lived 26 months, compared with 22 months for those on placebo. Three years later, 34% of vaccine patients were still alive, compared with 11% of unvaccinated patients. (Source: Reuters Health: Oncolink: February 2005.)