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A. Lane, E. S. Gragoudas, K. M. Egan; The Role of Sunlight in Progression of Ocular Melanoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4793.
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There is accumulating evidence that vitamin D is a protective factor in the pathogenesis of many cancers. We evaluated the influence of ultraviolet radiation (UVR) exposure, a surrogate measure of vitamin D exposure, on survival in patients with ocular melanoma.
A consecutive series of 2003 patients, diagnosed with uveal melanoma and treated with proton therapy between 1975 and 1986, were included in the analysis. Patients were followed through June 1999, with a median follow up among surviving patients of 10.0 years. A UVR score corresponding to each patient’s place of residence at the time of diagnosis was used as a measure of vitamin D-inducing UVR exposures. The UVR score is based on satellite imagining and ground level monitoring at stations throughout the US (http://www.cpc.ncep.noaa.gov/ products/stratosphere /uv_index). UVR index values range from low (2 or less) to extreme (12 or higher), and take factors which influence ground-level UVR, such as latitude, altitude and cloud cover, into account. Higher (erythemal) UVR levels are associated with a greater capacity for endogenous vitamin D synthesis. Cox regression analysis was performed to examine the relationship between UVR and melanoma-related mortality, while adjusting for established prognostic factors.
Overall, we observed no relationship between UVR score and mortality from eye melanoma. However, further analyses revealed strong interaction by iris color (P interaction=0.005), a surrogate for propensity to sunburn. Whereas higher (vitamin D-inducing) UVR scores were associated with a nonsignificant increase in death rates among lighter eyed persons (P trend for UVR score: P=0.05), a strong protective association was observed among persons with a darker iris. When compared to low ambient UVR (UVR scores<3), UVR scores of 6 or greater were associated with a significant 62% reduction in melanoma death rates (RR: 0.38; P=0.005) among brown-eyed persons. The inverse association was consistent in men (RR: 0.47; P=0.11) and women (RR: 0.26; P=0.02).
These findings provide some support for the hypothesis that vitamin D from sunlight exposure is a protective factor in the pathogenesis of eye melanoma.
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