Obesity and the Incidence of Upper Gastrointestinal Cancers: An Ecological Approach to Examine Differences across Age and Sex

BACKGROUND: Esophageal and gastric cancers differ in their epidemiology but have several risk factors in common. The aim of this study was to assess age and sex differences in the burden of esophageal and gastric cancers in the context of the global obesity epidemic. METHODS: Data from 50 countries were obtained from Cancer Incidence in Five Continents Volume X and GLOBOCAN 2012. Age-specific and age-standardized incidence rates of esophageal adenocarcinoma and squamous cell carcinoma (ESCC), as well as cardia (CGC) and noncardia (NCGC) gastric cancer, were estimated. Countries were grouped and analyzed according to their obesity prevalence. RESULTS: A gradient across quartiles of obesity prevalence was found for esophageal adenocarcinoma, with the highest incidence rates in high prevalence countries (ASR 3.0 vs. 0.8 per 100,000 in highest vs. lowest obesity quartiles, males). In contrast, for ESCC as well as for CGC and NCGC the reverse was true, with the highest rates observed in countries with the lowest obesity prevalence (ESCC, 2.2 vs. 11.5; CGC, 2.8 vs. 7.8; NCGC, 3.9 vs. 17.4 in highest vs. lowest obesity quartiles, males). Although for esophageal adenocarcinoma, sex and age differences in incidence were most pronounced in countries with a high prevalence of obesity, these differences were much smaller for the other cancer sites assessed. CONCLUSIONS: Variation in obesity prevalence may partly explain age and sex differences in the incidence of esophageal adenocarcinomas. IMPACT: Ecologic studies can help assess relationships between risk factors and cancer, and generate new hypotheses that may be pursued through more directed research.