Prostate cancer treatment shows promise
February 18 2005 12:00 AM ET
Doctors are reporting their first success at improving survival in men with advanced prostate cancer by using a treatment that trains the immune system to fight tumors. The approach is called a cancer vaccine although, unlike traditional vaccines, it treats the disease rather than prevents it. In a study of 127 men with advanced prostate cancer, those who got the vaccine lived an average of 4.5 months longer than those who were given a placebo. After three years, survival was 34% in the vaccine group and only 11% in the other. "That's a huge difference. These are people who have relatively few options, with limited survival," said Eric Small of the University of California, San Francisco, who led the study and gave results at a first-of-its-kind prostate cancer research meeting that opened Thursday in Orlando. The meeting is intended to bring more muscle to fighting the disease, which is the most common non-skin cancer in American men. About 230,000 new cases and 30,000 deaths from it are expected this year.
The vaccine, called Provenge, doesn't work like chemotherapy, and its side effects typically are limited to a couple days of fevers and chills, like what people feel when they are fighting off a cold. 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 in three infusions over a month.
In the study, men treated with Provenge survived an average of 26 months, compared with 21.4 months for those who received a dummy vaccine. After three years, 28 of the 82 men who got vaccine were alive while only five of the 45 in the placebo group were.
Philip Kantoff, a Harvard Medical School professor who heads prostate cancer treatment at the Dana-Farber Cancer Institute in Boston, and other specialists note that the study didn't achieve its primary goal of delaying the time when the disease worsened--something that could be expected if the vaccine were truly helping men live longer. "Time to progression is interesting but it isn't the gold standard. The gold standard is survival. We've improved survival," Small countered.
If a second study in about 100 men gives similar results later this year, Dendreon will seek Food and Drug Administration approval for Provenge, which already is being fast-tracked by the agency, said the company's president, Mitchell Gold. Dendreon also is testing Provenge for less serious cases of prostate cancer. Partial results from one such study are to be presented at the meeting on Saturday. (AP)