Feb. 17, 2005 -- A prostate cancer vaccine extends the lives of patients, even after all other treatments have failed.
In what doctors are calling a potentially "landmark" study, the vaccine, called Provenge, tripled the survival of men with advanced
Provenge is not a vaccine in the way that most people think of vaccines. Unlike most vaccines, which prevent diseases, this vaccine is used to treat men who already have prostate cancer.
Researcher Eric J. Small, MD, says this is the first nonchemotherapy drug treatment to improve survival. He presented the findings today at the first 2005 Multidisciplinary Prostate Cancer Symposium in Orlando, Fla.
Small, professor of medicine and urology at the University of California, San Francisco School of Medicine, says the treatment was far less toxic and better tolerated than chemotherapy. Provenge's only side effects were flu-like symptoms lasting just 24 hours.
Phillip Kantoff, MD, a medical oncologist at the Dana Farber Cancer Institute in Boston, calls the study a "potentially huge finding" and says it "represents the first vaccine approach in prostate cancer that shows a survival advantage."
The research involved 127 men, aged 47 to 85, with metastatic prostate cancer. None of the men had symptoms from the cancer, such as pain. The men no longer were responding to traditional
The men were divided into two groups -- 82 men received the Provenge prostate cancer vaccine, while 45 men were given a placebo vaccine. Three injections were given, two weeks apart.
Overall, Provenge prolonged life by as much as 4.5 months over those patients given the placebo vaccine.
Perhaps more significant were the results seen three years after the vaccine was given. At that point, 34% of vaccine patients were still alive compared with 11% of men that received the placebo vaccine.
Experts say it's important news for the more than 232,000 men diagnosed with prostate cancer each year in the U.S. It is the most common cancer among American men, killing some 30,000 each year.
The vaccine is still experimental and not yet available outside of clinical trials. Dendreon - the vaccine's maker - says the vaccine is being "fast-tracked" through the FDA. But it is still not likely to be up for approval until 2006 at the earliest. Results from additional trials are not expected until late 2005.
The vaccine itself was developed from each individual patient's cells, a process that began with a blood donation. The goal here was to "teach" the body to recognize and attack growing tumor cells.
As Small explains, the cells were processed to "enrich" the power of the patients' own immune cells to "search out target proteins that reside on the surface of 90%-95% of all prostate cancers." While most men can be successfully treated with surgery, radiation, and hormone therapy, for some, these treatments are simply not enough. Currently the only drug approved by the FDA for the treatment of advanced prostate cancer is Taxotere. But as promising as the new vaccine approach appears to be, experts point out it's still too early to determine the true benefit that may one day come from the vaccine.
Kantoff points out the study was relatively small, including only 127 men -- compared with a thousand or more who frequently participate in a single chemotherapy trial.
As a result, Kantoff says the positive findings could have been the result of "unforeseen biologic differences in the two groups." In this instance, factors related to each man's cancer and overall health might have actually been responsible for the outcome currently being credited to the prostate cancer vaccine.
The only way to know for sure, he says, is to duplicate the results in a much larger clinical trial --something the researchers are hoping to accomplish.
Still, Kantoff says the findings represent a major step forward in a potentially new and perhaps less toxic treatment for prostate cancer.
"The magnitude of the impact of this trial is remarkably large," he says, indicating that, if proven in larger trials, it could dramatically change prostate cancer treatment.