Vaccine Therapy Shows Promise in Prostate Cancer Patients

A vaccine therapy that stimulates the body’s own immune defenses is safe to give to prostate cancer patients early in the disease’s progression, a recent study found.

In the phase 2 clinical trial, published online December 19, 2014, in European Urology, researchers from the ECOG-ACRIN Cancer Research Group examined 2 investigational treatment options in adult patients with advanced prostate cancer who had undergone surgery or radiation and whose cancer resisted hormone therapy.

Patients in the first part of the study were treated with 1 cycle of PROSTVAC-V/TRICOM, a vaccine that primes the body’s immune system to respond to the prostate specific antigen (PSA) in the prostate tumor and improves the ability of immune cells to destroy their targets. These patients were give subsequent cycles of a similar vaccine, PROSTVAC-F/TRICOM. These vaccines were given in combination with GM-CSF, a drug that boosts the body’s immune system by stimulating the production of white blood cells. Six months after the first treatment, the researchers found that 25 of 40 eligible patients (63%) experienced no disease progression and minimal toxicity.

Patients in the second part of the study were treated with hormone therapy (androgen ablation) in addition to the PROSTVAC-VF/TRICOM combination. The researchers found that 20 of 27 eligible patients (74%) experienced a complete response at 7 months.

“Previous studies . . . have shown it is optimal to explore agents like PROSTVAC that harness the body’s own defenses in shutting down cancer,” said lead author Robert S. DiPaola, MD, in a press release.