A new immune-system therapy, called Provenge, recently approved by the U.S. Food and Drug Administration, may prolong a life and spare chemotherapy, with its debilitating side effects that are tougher to handle for older patients. Doctors hope the therapy at Mount Sinai Comprehensive Cancer Center in Miami Beach, the first South Florida facility to offer it, can become an important new weapon against several types of cancers. So far, the therapy is FDA-approved only for men with advanced, late-stage prostate cancer. Trials are under way to see if it also can help men newly diagnosed. Other trials are investigating whether the same concept --- boosting the body's immune system against cancer rather than fighting it with drugs --- might be useful against cancer of the bladder, breast, ovaries, colon and other organs.