Dietary polychlorinated biphenyls, long-chain n-3 polyunsaturated fatty acids and incidence of malignant melanoma

Background: For malignant melanoma, other risk factors aside from sun exposure have been hardly explored. Polychlorinated biphenyls (PCBs) mainly from fatty fish may affect melanogenesis and promote melanoma progression, while long-chain n-3 polyunsaturated fatty acids seem to exert antineoplastic actions in melanoma cells. Objectives: We aimed to assess the association of validated estimates of dietary PCB exposure as well as the intake of eicosapentaenoic acid and docosahexaenoic acid (EPA-DHA), accounting for sun habits and skin type, with the risk of malignant melanoma in middle-aged and elderly women. Methods: We included 20,785 women at baseline in 2009 from the prospective population based Swedish Mammography Cohort. Validated estimates of dietary PCB exposure and EPA-DHA intake were obtained via a food frequency questionnaire. Incident melanoma cases were ascertained through register-linkage. Results: During 4.5 years of follow-up, we ascertained 67 incident cases of melanoma. After multivariable adjustments, exposure to dietary PCBs was associated with four-fold increased risk of malignant melanoma (hazard ratio [HR], 4.0 [95% confidence interval {CI}, 1.2-13; P for trend = 0.02]), while EPA-DHA intake was associated with 80% lower risk (HR, 0.2 [95% CI, 0.1-0.8; P for trend = 0.03]), comparing the highest exposure tertiles with the lowest. Conclusion: While we found a direct association between dietary PCB exposure and risk of melanoma, EPA-DHA intake showed to have a substantial protective association. Question of benefits and risk from fish consumption is very relevant and further prospective studies in the general population verifying these findings are warranted. (C) 2016 Elsevier Ltd. All rights reserved.