Sun Exposure, Vitamin D, Prostate Cancer Study

[Neon Beach]

Sun Exposure, Vitamin D, Prostate Cancer Study

Description

Prostate cancer is the most common life threatening cancer among males in Canada and the second most common cancer cause of death in males. Despite its importance, relatively little is known about its etiology, and new hypotheses are urgently required. The objectives of this research project are to determine whether there is a inverse relationship between ultraviolet radiation exposure and risk of prostate cancer and whether there is evidence of a dose-response relationship between exposure and risk. The study will also determine whether exposure at a specific period of life is of particular importance. Ecological correlation studies have shown a relationship between latitude of residence, (a surrogate for ambient solar UV radiation exposure), and prostate cancer mortality. This is important because sun exposure is critical to the formation of vitamin D. Human intake of Vitamin D from foods is very modest, and over 85% of Vitamin D is synthesized from 7-dihydorocholesterol in the skin under the influence of UVB radiation in sunlight. Since there is a major public health thrust to reduce sunlight exposure to reduce risk of skin cancers, we may be inadvertently increasing risk of prostate and other tumours. The mechanism or pathway by which prostate cancer develops is likely to involve Insulin-like Growth Factors (IGF-1 and its binding protein, IGFBP-3), and the relationship between these factors and prostate cancer will also be examined. Preliminary data from a previous study of prostate cancer indicate that insulin resistance may increase risk of prostate cancer, and this investigation will attempt to confirm this relationship and quantify it. There is also evidence that a specific vitamin D receptor polymorphism may affect IGF-1 and IGFBP-3 levels, and ultimately risk for prostate cancer. This hypothesis will be tested.

700 men with histologically confirmed prostate cancer diagnosed from September 1, 2003 through February 28, 2007 will be selected from the BC Cancer Registry. A similar number of controls matched by age (within 5-year age groups) will be selected from the BC Ministry of Health Client Registry. All cases will be contacted by letter, and will be asked to participate in the study, which includes completion of a "life events calendar", a computer assisted telephone interview on sun exposure, and donation of a 40 cc blood sample.

Blood will also be used to undertake IGF and insulin resistance assays will be utilized to extract DNA to search for specific vitamin D receptor gene polymorphisms. DNA will also be stored at -86°C for future use. The current lack of information on causes of prostate cancer has rendered primary prevention extremely difficult. The study offers several new lines of investigation, which hold the hope of providing modifiable risk factors to reduce the population burden of prostate cancer in Canada.

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