Ambient ultraviolet radiation exposure and hepatocellular carcinoma incidence in the United States

Trang Vopham,Francine Laden,Rulla M Tamimi,Jian-Min Yuan,Kimberly A Bertrand,Jaime E Hart

doi:10.1186/s12940-017-0299-0

Abstract

BackgroundHepatocellular carcinoma (HCC), the most commonly occurring type of primary liver cancer, has been increasing in incidence worldwide. Vitamin D, acquired from sunlight exposure, diet, and dietary supplements, has been hypothesized to impact hepatocarcinogenesis. However, previous epidemiologic studies examining the associations between dietary and serum vitamin D reported mixed results. The purpose of this study was to examine the association between ambient ultraviolet (UV) radiation exposure and HCC risk in the U.S.MethodsThe Surveillance, Epidemiology, and End Results (SEER) database provided information on HCC cases diagnosed between 2000 and 2014 from 16 population-based cancer registries across the U.S. Ambient UV exposure was estimated by linking the SEER county with a spatiotemporal UV exposure model using a geographic information system. Poisson regression with robust variance estimation was used to calculate incidence rate ratios (IRRs) and 95% confidence intervals (CIs) for the association between ambient UV exposure per interquartile range (IQR) increase (32.4 mW/m2) and HCC risk adjusting for age at diagnosis, sex, race, year of diagnosis, SEER registry, and county-level information on prevalence of health conditions, lifestyle, socioeconomic, and environmental factors.ResultsHigher levels of ambient UV exposure were associated with statistically significant lower HCC risk (n = 56,245 cases; adjusted IRR per IQR increase: 0.83, 95% CI 0.77, 0.90; p < 0.01). A statistically significant inverse association between ambient UV and HCC risk was observed among males (p for interaction = 0.01) and whites (p for interaction = 0.01).ConclusionsHigher ambient UV exposure was associated with a decreased risk of HCC in the U.S. UV exposure may be a potential modifiable risk factor for HCC that should be explored in future research.

Highlights

Hepatocellular carcinoma (HCC), the most commonly occurring type of primary liver cancer, has been increasing in incidence worldwide
Using data from the underlying population from which HCC cases were sampled, HCC cases at the time of diagnosis resided in mostly urban counties (99.2%) where an average of 8.3% of the population engaged in heavy alcohol consumption, 23.9% smoked cigarettes, 25.7% were obese, and 11.4% had diabetes
Higher UV levels were observed in the Western U.S and parts of Louisiana, while lower UV levels were observed in the Northeastern and Midwestern U.S (Connecticut, Detroit, Iowa, Kentucky, New Jersey, and Seattle registries)

Summary

Introduction

Hepatocellular carcinoma (HCC), the most commonly occurring type of primary liver cancer, has been increasing in incidence worldwide. The purpose of this study was to examine the association between ambient ultraviolet (UV) radiation exposure and HCC risk in the U.S. Hepatocellular carcinoma (HCC) is the most commonly diagnosed histological type of primary liver cancer [1]. Vitamin D is a hormone acquired from sunlight exposure, diet, and dietary supplements that plays a major role in human health [9,10,11,12]. The few epidemiologic studies that have examined the association between dietary and serum vitamin D and liver cancer risk while adjusting for liver cancer risk factors have shown mixed results – inverse, positive, and null associations [16,17,18]

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