Dual therapy aids prostate patients

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Combining an anti-cancer vaccine with hormone-deprivation therapy seems to prolong the time before treatment failure in men experiencing a return of prostate cancer, a new federal study suggests.

Scientists at the National Cancer Institute say more research is needed before they can say such combination therapy prolongs disease-free survival of prostate cancer patients.

"This is a preliminary study, but it's definitely promising," said Dr. Philip M. Arlen of NCI's Laboratory of Tumor Immunology and Biology, lead investigator in the study published in the August issue of Journal of Urology.

The NCI research is the first to combine therapy involving a reduction in levels of androgen, a male sex hormone, and a vaccine for prostate cancer.

Dr. Arlen said the results of the Phase 2 efficacy trial suggest that this combination treatment benefits men who have been resistant to androgen-deprivation therapy in the past and who go on to experience a rise in prostate-specific antigens (or PSAs), which can indicate recurrence.

"We're seeing this population much more frequently today than we did in the past," Dr. Arlen said. He explained that they are men with elevated PSA levels, who have not shown evidence of cancer spread in CT scan procedures.

"These guys feel great," because they have not developed prostate cancer symptoms, he said. The goal of the NCI researchers is to "hold them off" from having their cancer return, so they can enjoy a better quality of life.

Dr. Arlen and his team noted that prostate cancer often progresses after treatment with hormone-deprivation therapy. Their thinking was that adding the vaccine would help strengthen the body's natural defenses against this cancer.

The American Cancer Society says prostate cancer is the second-most-common type of cancer found in American men, after skin cancer. The society estimates that 232,000 new cases will be diagnosed this year and that 30,350 men will die of the disease.

For the study, NCI scientists randomly assigned 42 prostate cancer patients to receive either the experimental vaccine or a second-line anti-androgen treatment, consisting of the hormone nilutamide.

Nilutamide works by blocking the effects of excess testosterone, a hormone that can promote the growth of cancer cells.

After the first six months of the study, all participants who still had rising PSA levels, but no evidence of cancer metastasis, could choose to receive both treatments, rather than just one.

The median time before treatment began to fail was 9.9 months for men who got the vaccine only. Those on only nilutamide failed after an average of 7.6 months.

But 12 of the 21 vaccine recipients in the study requested that nilutamide be added to their treatment after six months. Those patients experienced an additional median time of 13.9 months before treatment failed, for a total of 25.9 months from the start of their treatment.