Vitamin D impact on prostate cancer

Researchers at the Oregon Health & Science University in the US on Thursday announced the launch of a national study to investigate the effect of high-dose vitamin D in combination with the chemotherapy agent docetaxel (Taxotere), for patients with advanced prostate cancer.

The ASCENT (AIPC Study of Calcitriol Enhancing Taxotere) study is a multicentre, randomised, double-blind trial based on the results of a preliminary study in Oregon. ASCENT will determine whether a high dose of an active form of vitamin D, called calcitriol, taken once a week in combination with docetaxel, is any more effective than docetaxel alone for patients with androgen-independent prostate cancer (AIPC), an advanced form of prostate cancer.

"Late-stage prostate cancer patients have few treatment options, and we are cautiously hopeful that this study will further confirm and extend the promising results we've already seen with docetaxel in combination with high-dose pulse administration (HDPA) calcitriol,"​ said OHSU Cancer Institute oncologist Tomasz Beer, study chairman and assistant professor of medicine (hematology and medical oncology) in the OHSU School of Medicine.

The study will enroll approximately 232 patients at about 20 medical centres in the United States, including OHSU. Additional sites will be added during the next several months.

The study hopes to achieve a reduction of 50 per cent or more in prostate specific antigen (PSA) levels in patients. 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, many clinicians use elevated PSA levels as an indicator of disease progression.

Results from the initial OHSU study were presented by Beer at the American Society of Clinical Oncology conference last May. In that trial, 81 per cent (30 of 37) of patients treated with HDPA calcitriol in combination with docetaxel had a reduction in PSA levels of more than 50 per cent. Four other studies of docetaxel without calcitriol have reported that 38 to 46 per cent of the patients had more than a 50 per cent reduction in PSA levels, about half the rate as those patients on the combination therapy.

Prostate cancer is the most common cancer in men, with approximately 189,000 new cases diagnosed and roughly 30,200 deaths in the United States each year (2002 Cancer Facts and Figures, American Cancer Society).

Further information on the study can be obtained from Martin Munguia at the Oregon Health & Science University: munguiam@ohsu.edu