Intake of Furocoumarins and Risk of Skin Cancer in 2 Prospective US Cohort Studies.

Background: In prior studies, higher citrus consumption was associated with higher risk of cutaneous malignant melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC). Furocoumarins, compounds with phototoxicity and photocarcinogenicity in citrus, may be responsible for the association. Objectives: The objective of the study was to investigate the association between furocoumarin intake and skin cancer risk. Methods: A total of 47,453 men from the Health Professionals Follow-Up Study (HPFS) and 75,291 women from the Nurses' Health Study (NHS) with diet data collected every 2-4 y in the 2 prospective cohort studies were included. A furocoumarin food composition database for 7 common furocoumarins Ibergaptol, psoralen, 8-methoxypsoralen, bergapten, 6',7'-dihydroxybergamottin (6'7'-DHB), epoxybergamottin, and bergamottin1 was developed and used to calculate participants' cumulative average and energy-adjusted furocoumarin intake. Multivariate HRs and 95% C Is of the associations between furocoumarin intake and skin cancer risk were estimated using Cox proportional hazards models. Analyses were performed separately in each cohort as well as pooled using a fixed-effects model. Results: Throughout follow-up (1984-2012 in the NHS and 1986-2012 in the HPFS), we identified 1593 melanoma, 4066 SCC, and 28,630 BCC cases. Higher intake of total furocoumarins was associated with an increased risk of BCC; the pooled HR comparing the top with the bottom quintile was 1.16 (95% CI: 1.11, 1.21; P-trend = 0.002). Higher intakes of bergaptol, bergapten, 6'7'-DHB, and bergamottin were also significantly associated with increased BCC risk. No significant associations were found between intake of total furocoumarins and the risks of SCC or melanoma. Conclusions: Intakes of total furocoumarins as well as some individual furocoumarins were associated with an increased risk of skin cancer, especially BCC, in 2 cohorts of US health professionals.