A Seattle biotechnology company recently reported success in extending survival in men with advanced prostate cancer in two clinical trials of its investigational immunotherapy treatment. Men who received the drug — Provenge — showed three-year survival rates more than twice those of patients receiving a placebo.
"This is the first time that an immunotherapy trial in a solid tumor has shown an improvement in survival," said Dr. Tia Higano, a prostate-cancer specialist at the Seattle Cancer Care Alliance and an investigator for the Dendreon Corporation, the maker of Provenge. "Although chemotherapy has been shown to have a very modest survival benefit, it can have numerous unpleasant side effects. Provenge, which has few side effects, may be a reasonable treatment option for men who do not yet have symptoms." Higano presented the trial data at a European cancer conference in late October.
Phase III studies
The combined results from both double-blind, Phase III studies showed that Provenge recipients had a 23.2-month median survival benefit, as opposed to 18.9 months with placebo — a 23 percent improvement in median survival. Of 147 men given the drug, 33 percent were still alive three years later, compared with 15 percent who took a placebo.
Provenge is designed to stimulate the immune system to attack cells that express a certain type of protein found on about 96 percent of prostate-cancer cells. Dendreon plans to seek approval for the treatment from the U.S. Food and Drug Administration; decisions usually take about a year. If approved, Provenge will be the first cancer immunotherapy vaccine proven to work.
Chemotherapy, the standard late-stage therapy for prostate cancer, is often accompanied by nausea, hair loss and anemia. In contrast, Provenge is well tolerated and its most common side effects are fever and chills for one or two days. In the studies, patients typically received three infusions over a one-month period as a complete course of therapy.
"Because Provenge is safe and well tolerated, it appears to be a reasonable alternative to chemotherapy in men who otherwise have no symptoms. Chemotherapy can be reserved for a later time," said Higano, who is also an associate professor of medicine at the University of Washington. More than 1 million men in the United States have prostate cancer, with about 220,000 new cases diagnosed each year. The cancer usually develops slowly, so many men will die with this cancer rather than from it. However, about 30,000 men die from the disease each year.
"The results of the combined data from these two trials is an exciting advance for men with prostate cancer because of the hope for less toxic therapy that will improve survival," Higano said. "It is potential new weapon against prostate cancer."
