For the first time, researchers have found that a novel immunologic therapy increases survival by nearly 18 percent in men with advanced prostate cancer that no longer responds to hormone therapy.
The therapeutic cancer vaccine, called APC8015 (Provenge), is likely to become a new standard of care for patients with metastatic prostate cancer. The UCSF-led study is the first to demonstrate a survival benefit from immunologic therapies or vaccines in patients with advanced prostate cancer.
"We're very pleased with the results. A therapy that prolongs life yet avoids the side effects of other therapeutic approaches is clearly attractive to patients and physicians alike," said Eric Small, MD, UCSF professor of medicine and urology and lead investigator of the study.
The study will be presented in Orlando, Florida, on Saturday, Feb. 19, at a prostate cancer symposium sponsored by the American Society of Clinical Oncology, the Prostate Cancer Foundation, the American Society for Therapeutic Radiology and Oncology, and the Society of Urologic Oncology.
Although the new agent is called a vaccine, it is not designed to prevent cancer. Rather, it uses the patient's own immune system to recognize and attack existing cancer cells. APC8015 is designed to stimulate the immune system to attack cells that express prostatic acid phosphatase (PAP), a protein found on approximately 95% of prostate cancer cells.
APC8015 is produced by collecting blood from each patient, isolating the relevant immune cells, and stimulating those cells so that they recognize PAP as "foreign." The resulting product, APC8015, is administered as an intravenous infusion.
In this study, investigators randomized 127 men with asymptomatic metastatic prostate cancer that no longer responded to hormone therapy to receive the vaccine (82 men) or a placebo (45 men). Patients received three doses of the vaccine at two-week intervals, and were followed for three years.
Overall survival among patients receiving the vaccine was 25.9 months, compared to 22 months in the placebo group. Three years later, more than three times as many vaccine patients (34 percent) were still alive, compared to the placebo group (11 percent). Treatment was well-tolerated - fever and shaking were reported as the most common side effects, and generally disappeared within two days of vaccine administration.
Therapeutic vaccines are being studied in the treatment of other types of cancer including lymphoma, leukemia, and cancers of the brain, breast, lung, kidney, ovary, pancreas, colon, and rectum.
In 2004, 26,000 men in the US died of prostate cancer. Prostate cancer is the most often diagnosed non-skin cancer in the US and the third most-common cancer worldwide, according to the American Cancer Society. Of the 185,000 men diagnosed each year in the US, an estimated 10-15 percent already have metastatic disease at the time of diagnosis, and another estimated 20 percent will develop metastatic disease.
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