Vaccine Slows PSA Increase in Hormone Refractory Prostate Cancer
Results from a study of 19 men with hormone refractory prostate cancer indicate that an experimental cancer vaccine produces an immune response, appears to be safe, and may slow the rate of increase of prostate specific antigen (PSA). These findings were published in the British Journal of Cancer.
The prostate is a gland of the male reproductive system. It produces some of the fluid that transports sperm during ejaculation. After skin cancer, prostate cancer is the most common form of cancer diagnosed in men. The outlook for men diagnosed with prostate cancer is good since overall survival rates for all stages of prostate cancer have improved dramatically over the past 20 years.
Current treatment options for prostate cancer include watchful waiting, surgery, chemotherapy, radiation, or hormonal therapy. Hormonal therapy is designed to block testosterone from stimulating the growth of hormone-dependent types of prostate cancer.
Some prostate cancers become resistant to hormonal therapy and then require a different treatment approach; this condition is known as hormone refractory prostate cancer. Since hormone refractory prostate cancer can be difficult to treat, novel approaches such as cancer vaccines are being explored. The goal of these vaccines is to produce an immune response that helps the body fight cancer cells.
To assess the effect of an experimental cancer vaccine among men with hormone refractory prostate cancer, researchers in Norway conducted a phase I/II clinical trial among 19 prostate cancer patients. All the patients had evidence of cancer progression during treatment with hormonal therapy, indicating a lack of response to hormonal therapy. Fourteen of the patients had evidence of bone metastases at the start of the study.
The primary objectives of the study were to assess safety and immune response to the vaccine. Researchers also collected the following information about how the cancer responded after vaccination:
- Twelve out of 19 patients showed evidence of an immune response to the vaccine.
- There were changes to measures of PSA that suggested a possible clinical benefit of the vaccine.
- While most of the men continued to experience a rise in PSA after vaccination, the rate of PSA increase (PSA velocity) slowed after vaccination in 13 out of 19 patients.
- There was no evidence of an improvement in bone metastases after vaccination.
- There were no serious adverse effects of vaccination.
The researchers conclude that the vaccine is safe and produces an immune response in a majority of patients. The researchers note that the change in PSA velocity that occurred after vaccination “suggests that this approach may become useful as a treatment modality for prostate cancer patients.”
Patients with prostate cancer may wish to talk with their doctor about the risks and benefits of participating in a clinical trial further evaluating promising therapeutic approaches. Two sources of information regarding ongoing clinical trials include the National Cancer Institute (www.cancer.gov) and www.cancerconsultants.com.
Reference: Mu LJ, Kyte JA, Kvalheim G et al. Immunotherapy with allotumor mRNA-transfected dendritic cells in androgen-resistant prostate cancer patients. British Journal of Cancer. 2005;93:749-756.
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