Prostate Cancer Vaccine and Hormone Treatment
Can a combination of prostate cancer vaccine and hormone treatment help patients? The results of the first study to combine antiandrogen therapy and a cancer vaccine saw an increase in the time hormone therapy was started until the treatment no longer worked. Although more research is needed, it seems likely that a prostate cancer vaccine and hormone treatment combination is helpful for patients whose disease has recurred.
A new study finds that a cancer vaccine combined with hormone-deprivation therapy can help patients with recurrence of prostate cancer. The results of this clinical trial appear in the August 2005 issue of the Journal of Urology.
This phase II trial (a trial that usually tests the effectiveness of a drug) was designed to treat patients with nonmetastatic prostate cancer who were experiencing rising levels of prostate-specific antigen (PSA), which can indicate recurrence of the disease. Prostate cancer often progresses for several years after treatment with hormone-deprivation therapy.
This is the first study to combine antiandrogen therapy (reducing the amount of androgens, which are male sex hormones) and a cancer vaccine for treating prostate cancer, and is also the first randomized clinical trial in this population of prostate cancer patients. Cancer vaccines are designed either to treat existing cancers or to prevent the development of cancer. The experimental prostate cancer vaccine used in this study was designed to strengthen the body's natural defenses against the disease.
This study was designed to answer the question regarding what to do for someone for whom prostate cancer hormone therapy is no longer working.
Researchers randomly assigned 42 patients with prostate cancer to receive either vaccine or second-line antiandrogen treatment, which consisted of the hormone nilutamide. Nilutamide works by blocking the effects of excess testosterone, a hormone produced by the body that can promote the growth of cancer cells. After the first six months of treatment, participants in both arms of the study -- who had rising PSA levels but no evidence of metastatic disease -- could choose to receive the other treatment in combination with their first study treatment.
There were no serious side effects from the vaccine, but some of the participants receiving nilutamide experienced severe adverse reactions involving lung toxicities, an uncommon side effect sometimes associated with the drug.
The average time before the treatment started to fail was 9.9 months for individuals who received vaccine alone, compared to 7.6 months for patients on nilutamide alone -- a difference not considered statistically significant. However, 12 of the 21 vaccine recipients had nilutamide added to their treatment regimens after six months. The patients in that group experienced an additional median time of 13.9 months until treatment failure, for a total of 25.9 months from the beginning of their treatments.
The positive effects of combining antiandrogen therapy with vaccine may be because the vaccine acts to "prime" the immune system, and when the hormone treatment was added, it allowed the vaccine to work even better. The study indicates that there may well be a synergy between immunotherapy with vaccines and hormone deprivation.