March 31st, 2010

Preliminary Results Indicate that an Investigational Vaccine May Extend Survival in Hormone-resistant Prostate Cancer


The investigational vaccine known as PROSTVAC-VF appears to significantly prolong survival in patients with metastatic hormone-resistant prostate cancer, according to the results of a Phase II study published in the Journal of Clinical Oncology.1

The prostate is a male sex gland responsible for producing fluid that forms semen. It is located below the bladder, in front of the rectum, and surrounds the urethra. Prostate cancer occurs when the cells in the prostate gland grow out of control.

Prostate cancer is a hormonally sensitive disease that can be controlled for long periods with androgen deprivation therapy (ADT). When prostate cancer stops responding to this treatment is it referred to as hormone refractory (or castration-resistant) prostate cancer. Metastatic, hormone-refractory prostate cancer is a challenging form of the disease to treat because the cancer has spread to distant sites in the body and does not respond to treatment with hormonal therapy.

PROSTVAC-VF is an investigational cancer vaccine that is designed to stimulate the immune system to attack targets found on cancer cells.

A double-blind, Phase II study included 122 patients with metastatic hormone-resistant prostate cancer who were randomly assigned to receive PROSTVAC-VF (82 patients) or placebo (40 patients). The primary endpoint of the study was progression-free survival, which was shown to be similar between the two groups. However, three years following the study, the median overall survival was significantly longer in the vaccine group (25.1 months) compared with the placebo group (16.6 months).

The vaccine was well-tolerated, with most adverse events being injection site reactions. The researchers concluded that PROSTVAC-VF was associated with a 44% reduction in death rate and an 8.5-month improvement in median overall survival. These data will need to be confirmed in a larger, Phase III study.


1 Kantoff PW, Schuetz TJ, Blumenstein BA, et al. Overall survival analysis of a phase II randomized controlled trial of a poxviral-based PSA-targeted immunotherapy in metastatic castration-resistant prostate cancer. Journal of Clinical Oncology. 2010; 28: 1099-1105.

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