Researchers say the compound, called APC8015 (Provenge), primes patients’ immune systems to recognize and kill prostate cancer cells that have spread throughout the body.In a trial of 127 men with advanced disease, patients given the vaccine, called Provenge, experienced an average 18 percent increase in survival, compared to those on a placebo, the scientists report.”For those of us doing research into metastatic prostate cancer, it looks pretty great,” said study co-researcher Dr. Celestia Higano, an assistant professor of medicine and urology at the University of Washington in Seattle.”We prolonged survival — that’s great news. It’s the first time we’ve seen it with a vaccine in this cancer,” she added.
She and her colleagues presented the findings Thursday at this year’s Multidisciplinary Prostate Cancer Symposium in Orlando, Fla.Besides promising a potential boon to people struggling with this cancer, the therapy gives “proof of principle” to the idea that immune-based treatments can have a real impact on prostate cancer and other malignancies, experts said.”There have been many failures with this kind of approach, and many have wondered if we shouldn’t set the bar lower, somehow lower our expectations, and not hope for extended survival,” said Dr. Bruce Roth, a prostate cancer researcher at Vanderbilt University in Nashville, Tenn.
When caught early, prostate cancer remains very curable. However, despite advances in early detection, the disease remains the second leading cancer killer of U.S. men, according to the American Cancer Society. Even among men who develop the disease while it is still confined to the prostate, between 30 percent to 40 percent will experience a recurrence in years to come, experts say.Because prostate cells depend heavily on testosterone to grow, therapies that reduce levels of circulating testosterone are often the first course of action in men who experience a recurrence. However, prostate cancer cells gradually grow resistant to hormonal therapy, so relapse is almost inevitable.
Until very recently, doctors could only offer patients palliative therapies once that relapse set in.”The vaccine is composed of a person’s own immune cells that have been isolated from the blood and then sensitized to prostatic acid phosphotase, which is found on 95 percent of prostate cancer cells,” Higano explained. These cells “are then infused back into the patient.”Once inside the patient, these sensitized cells prime the patient’s immune system to recognize and destroy prostate cancer cells roaming throughout the body, Higano said.The Seattle study involved 127 men with cancer that had spread beyond the prostate and grown resistant to hormonal therapy. Eighty-two of the men received Provenge, while the other 45 received a placebo.