Study: Vaccine approach extends life of metastatic prostate Ca patients

Patients with metastatic prostate cancer who received a vaccine engineered to spur an immune system attack on prostate tumor cells lived substantially longer than patients who received a placebo vaccine, according to researchers at Dana-Farber Cancer Institute, Boston and affiliated organizations.

The randomized phase II study, published online in the Journal of Clinical Oncology (Jan. 25, 2010), involved the PROSTVAC-VF vaccine, a combination of two weakened poxviruses that have been genetically programmed to produce slightly irregular versions of PSA and three costimulatory molecules that spur the immune system to a more vigorous attack on tumor cells.

The double-blinded trial included 125 patients with metastatic prostate cancer who did not respond to standard, hormone-lowering therapy. Eighty-two of the participants received the vaccine and 40 received placebo.

After 3 years, 30% of the PROSTVAC-VF patients were alive versus 17% of the control group. The median survival of the vaccine group was 24.5 months, compared with 16 months for the control group, an 8.5-month increase. Patients tolerated the vaccine well; only a small number experienced side effects such as fatigue, fevers, and nausea.

"Although this study is relatively small, it offers encouraging evidence of a clinically meaningful benefit from this vaccine approach," said principal investigator and lead author Philip Kantoff, MD, of Dana-Farber Cancer Institute.

Investigators are planning a phase III trial that will enroll about 600 patients to further evaluate the vaccine’s effectiveness.