A Prospective Study of Toenail Trace Element Levels and Risk of Skin Cancer
A partir de données des cohortes "the Nurses’ Health Study" et "the Health Professionals Follow-Up Study" incluant 6 708 femmes et 3 730 hommes (durée de suivi : 26-28 ans), cette étude analyse l'association entre le taux des métaux cancérogènes (mercure, sélénium, chromium, fer et zinc) mesurés dans les ongles des orteils et le risque de cancer de la peau
Background : Few epidemiologic studies have investigated trace element exposure and skin cancer risk. Methods : Toenail levels of mercury, selenium, chromium, iron, and zinc were measured from 6,708 women in the Nurses' Health Study (1984-2012) and 3,730 men in the Health Professionals Follow-up Study (1986-2012) with data from prior nested case-control studies. Participants were free of skin cancer at toenail collection and followed for incident basal (BCC) and squamous cell carcinoma (SCC), and melanoma. Cox proportional hazards models were used to compute hazard ratios (HR) and 95% confidence intervals (CI) of skin cancer associated with the elements in each study. We calculated pooled multivariable HRs using a fixed-effects model. During 26-28 years of follow-up, 2,433 BCC, 334 SCC, and 130 melanoma cases were documented. Results : Higher toenail mercury levels were associated with risk of BCC (pooled HR for top versus bottom quintiles = 1.34 [95% CI 1.18-1.52], P trend < 0.0001). Similar direct associations were found with risks of SCC (pooled HR for top versus bottom quartiles = 1.41 [95% CI 1.03 - 1.94], P trend =0.04) and melanoma (pooled HR for top versus bottom quartiles = 1.88 [95% CI 1.12 - 3.16], P trend =0.02). Chromium was positively associated with BCC in females only. No associations were found between other metals and skin cancer risk. Conclusions : Our prospective data found that increased toenail mercury concentrations were associated with increased skin cancer risk. Impact : If our novel findings are confirmed, mercury may play a role in skin carcinogenesis.