SAN FRANCISCO -- Today, a University of California, San Francisco professor will report on a new treatment for men with advanced prostate cancer.

Dr. Eric Small says the treatment trains the immune system to fight tumors. It's called a cancer vaccine although unlike traditional vaccines, it treats disease rather than prevents it.

In a study of 127 men with advanced prostate cancer, those who got the vaccine lived an average of 41/2 months longer than those who were given fake treatments. After three years, survival was 34 percent in the vaccine group and only 11 percent in the other.

Dr. Small says "That's a huge difference. These are people who have relatively few options, with limited survival". He led the study and will give results at a first-of-its-kind prostate cancer research meeting that opens today in Orlando. Prostate cancer 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.