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Study Shows Benefits of Adding High-Dose Vitamin D to Chemotherapy for Advanced Prostate Cancer

   ORLANDO, Fla.

Calcitriol may safely double effectiveness of Taxotere® treatment

The addition of high-dose calcitriol to weekly treatment with the chemotherapy agent docetaxel (Taxotere®) appears to improve the therapeutic response in men with hormone-refractory prostate cancer without compromising safety, according to results reported at the 38th Annual Meeting of the American Society of Clinical Oncology (ASCO). Calcitriol is the active form of vitamin D.

Data from a phase II clinical trial suggest as much as twice the efficacy with the docetaxel/calcitriol combination than docetaxel alone, as measured by prostate-specific antigen (PSA) response rate. The study showed that 81 percent of patients treated with the combination regimen cut their PSA levels by more than half. Studies of docetaxel without calcitriol have reported a 42 percent PSA response rate overall. PSA is a substance produced within the prostate gland, and a high PSA level may indicate the presence of cancer. In patients with advanced prostate cancer, PSA correlates with the amount of cancer in the body.

"Because there is no standard treatment for hormone-refractory prostate cancer, new therapeutic strategies are clearly needed," said Tomasz Beer, M.D., an oncologist at the Oregon Health & Science University (OHSU) Cancer Institute in Portland, Oregon, and lead investigator of the study. "Docetaxel used alone has shown promise in treating prostate cancer, and our new data strongly indicate that the favorable results can be enhanced with the addition of high-dose vitamin D."

The study included 37 men with hormone-refractory prostate cancer, or disease that was progressive despite standard hormonal therapy, including anti-androgen withdrawal. In addition to PSA response, eight of 15 men with measurable disease responded with significant reductions of their tumors.

Patients in the study received oral calcitriol, 0.5 mcg/kg, (micrograms) on the first day of the treatment cycle, followed by an infusion of docetaxel, 36 mg/m2, on the following day. The treatment was repeated weekly for six weeks of an eight-week cycle until there was evidence of disease progression or unacceptable toxicity, or until the patient requested to be withdrawn from the study.

The results of this phase II study are now the basis for a future phase III study to be conducted at OHSU and other institutions. That randomized study will evaluate the use of weekly docetaxel versus weekly docetaxel plus calcitriol in hormone-refractory prostate cancer.

Prostate cancer is the most common malignancy among men and the second leading cause of cancer death in men in the United States. The American Cancer Society estimates that in 2002, approximately189,000 men will be diagnosed with the disease, and about 32,200 will die of it. Overall, roughly one in six American men will develop prostate cancer during his lifetime. If detected early, however, treatment can be highly effective.

Oregon Health & Science University is a health and research university focused on improving the well-being of people in Oregon and beyond. OHSU educates health practitioners, bioscientists, high-technology professionals, and environmental scientists and engineers, and it undertakes the indispensable functions of patient care, community service and biomedical research.

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