Melanoma risk factors within the prostate, lung, colorectal, and ovarian cancer screening trial

Melanoma is among the leading causes of cancer death in younger adults. Established risk factors are mostly nonmodifiable with the exception of exposure to ultraviolet radiation. Because melanomas are not limited to areas of the body that are exposed to ultraviolet radiation and because other risk factors do not account for many cases of melanoma, it is expected that there are yet unidentified risk factors. Overall, melanoma incidence rates continue to rise despite efforts to educate people about the risk of sun exposure and tanning beds. This increase combined with the aggressive and dangerous nature of melanoma in advanced stages has fueled campaigns for prevention and early diagnosis. When caught early, melanoma treatment is relatively successful when treated with surgery. The present study evaluates risk factors that have been suggested by previous research done primarily on non-U.S. populations. These include vitamin D levels, body mass index, and height. The databases in some European countries are extensive and have provided a platform to investigate these risk factors. The limitations of this thesis are few but important. Germaine to proving the necessity of this study is the limitation that the cohorts are very geographically narrow. The Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer cohort provides a large and geographically diverse U.S. population for this study. It enrolled and followed over 150,000 people for 13 years each to evaluate the efficacy of screening for each of the 4 cancer types. Incidence of all other cancer types were also recorded but not studied as they are not the primary aims of the PLCO. In this review of the data provided by the PLCO, the following associations or lack thereof were found: High self-reported vitamin D intake seemed to predict an increased risk of melanoma among men but not women. There was no dose response curve or trend between reported vitamin D intake and melanoma risk. Serum vitamin D levels did not seem to predict disease severity as measured by tumor thickness. There was an interesting correlation between melanoma risk and body mass index (BMI) calculated from reported height and weight at age 20. In men, being underweight at age 20 seemed to be protective while in women being overweight at age 20 seemed to be protective. BMI did not correlate with disease severity as measured by tumor thickness. Height seemed to be correlated to melanoma risk. There was significant trend between increasing height and melanoma risk in men and women. Those in the highest quartile of height were at a significantly increased risk compared to those in the lowest quartile. In summary, this analysis of PLCO data confirms the difficulty of identifying risk factors for melanoma. We corroborated the finding that height is positively correlated with melanoma risk; however, BMI and vitamin D findings were not as clear.