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Immunotherapy for Metastatic Prostate Cancer Explored

Researchers say vaccine trial suggests 'clinically meaningful benefit' and plan further research

FRIDAY, Jan. 29 (HealthDay News) -- Treatment with a prostate-specific antigen (PSA)-targeted poxviral vaccine substantially improves overall survival among metastatic prostate cancer patients, according to the results of a phase II study published online Jan. 25 in the Journal of Clinical Oncology.

Philip W. Kantoff, M.D., of the Dana-Farber Cancer Institute in Boston, and colleagues conducted a blinded study in which patients with minimally symptomatic castration-resistant metastatic prostate cancer (mCRPC) were randomized to treatment with either the PSA-targeted poxviral vaccines made up of two recombinant viral vectors encoding transgenes for PSA, and three immune costimulatory molecules (PROSTVAC-VF), plus granulocyte-macrophage colony-stimulating factor, or placebo immunotherapy with empty vector vaccinia, subsequent boosts with empty vector fowlpox, and saline injections.

At three-year follow-up, the researchers found that 30 percent of the patients receiving the PROSTVAC-VF were still living compared to 17 percent of the control group. The PROSTVAC-VF group had 8.5 months longer median survival compared to the control group (25.1 versus 16.6 months).

"PROSTVAC-VF immunotherapy was well tolerated and associated with a 44 percent reduction in the death rate and an 8.5-month improvement in median overall survival in men with mCRPC. These provocative data provide preliminary evidence of clinically meaningful benefit but need to be confirmed in a larger phase III study," the authors write.

Several study authors reported financial ties to ImmunoTherapeutics and Therion Biologics. These two companies have had collaborative research and development agreements with the National Cancer Institute, which provided funding for the study.

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