Sept. 6, 2008 – According to the National Cancer Institute (NCI), new research indicates that giving prostate cancer patients a continuous low dose of an immune system booster (known as “metronomic dosing”) is not only safe, but also produces similar immune responses and fewer side effects than the more common dosing method, which is not well tolerated by many patients.

Men with Localized Prostate Cancer, Candidates for Radiation Therapy
The vaccine used in the study was designed to stimulate an immune response against prostate-specific antigen (PSA), a protein produced by the prostate that is often found at elevated levels in the blood of men who have prostate cancer.

In the study, researchers examined the side effects and immune responses of patients treated with a three-pronged approach: the vaccine, radiation therapy, and an alternative dosing regimen of an immune system booster, interleukin-2 (IL-2). The patients all had localized prostate cancer, had not undergone surgery to remove the prostate, and were candidates for radiation therapy as their primary form of treatment.

In a previous study involving the same prostate cancer vaccine, IL-2 was given to 19 patients daily for five days during each 28-day vaccine treatment cycle, and a large majority of the patients had to have the dose of IL-2 reduced or discontinued, primarily because of fatigue.

Goal is to Decrease Side Effects
In this new study, the researchers sought to decrease the side effects associated with IL-2. To do this, the team treated 18 patients with the vaccine and radiation therapy, but with lower doses of IL-2 given over a longer period of time. The patients received the same total amount of IL-2 as in the previous study, but it was administered in smaller daily doses for 14 days of each 28-day treatment cycle.

With metronomic dosing, less than a quarter of the patients had side effects that required their dose of IL-2 to be reduced.

Metronomic Dosing Increased Immune Response
The research team also found that metronomic dosing of IL-2 produced effects on immune cell populations and immune responses that were similar to those observed previously with the standard dosing method. Five of eight evaluated patients had at least a three-fold increase in immune cells that were directed against PSA. The researchers also noted that, similar to the standard dosing method, metronomic dosing of IL-2 induced immune responses against other prostate cancer antigens in some patients.

According to James L. Gulley, MD, PhD, of NCI’s Center for Cancer Research, "Based on safety and feasibility, metronomic dosing appears to be superior to standard dosing and administration," although he also stated that "more research is needed to evaluate the efficacy of this dosing method in treating prostate cancer."

The study, led by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, was published in the August 15, 2008, issue of Clinical Cancer Research.

This overview is drawn from information furnished by the National Cancer Institute, “Alternative Vaccine Strategy Shows Promise in Prostate Cancer Patients”.

For further information: “Combining a recombinant cancer vaccine with standard definitive radiotherapy in patients with localized prostate cancer,” J.L. Gulley, et al, Clinical Cancer Research, November 2005.

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For more information on vaccines and prostate cancer, see Alternative Vaccine Strategy Shows Promise in Prostate Cancer Patients.

If you're experiencing side effects from prostate cancer treatments, see Advice to Help You Cope with Side Effects of Prostate Cancer Treatments.