The purpose of this study is to investigate the therapeutic effect and the safety of
high-dose vitamin D supplementation in metastatic colorectal cancer patients. We propose to
supplement metastatic (stage 4) colorectal cancer patients with oral doses of vitamin D to
raise serum 25-hydroxy-vitamin D [25(OH)D] levels to the high normal range of 200-250 nmol/L.
The primary objective of this study is to evaluate the metabolic consequences, including
tolerability and toxicity, of prolonged, high-dose physiological vitamin D in patients with
colorectal cancer. The secondary objective is to evaluate patient survival with regards to
high-dose vitamin D supplementation.
Hypothesis:
Whereas low doses of vitamin D reportedly play a significant role in prevention of colorectal
cancers, do much larger (pharmacological) doses of vitamin D have a significant therapeutic
effect against the same kind of cancer?