Racial Differences in the Effect of Alcohol and Tobacco on the Risk of Esophageal Squamous Cell Carcinoma

Abstract

Purpose: Within the U.S., African and Asian Americans have higher incidences of esophageal squamous cell carcinoma (ESCC) than whites. Alcohol and tobacco use are well-established risk factors for ESCC. We hypothesized that the effects of these exposures are stronger among individuals of Asian or African descent than among those of European descent. Methods: We performed a systematic literature review in electronic databases regardless of language. Eligible studies were population-based assessments of the effect of tobacco and/or alcohol on the risk of ESCC, and allowed for stratification by race. Quality of studies was assessed by the Newcastle-Ottawa Scale. Meta-analyses were performed to identify summary estimates using random effect models. Heterogeneity was defined by Cochrane's Q p<0.20 and the inconsistency index (I2, < 25% low, > 75% high). Results: Systematic review identified 4,951 unique citations, of which 39 were eligible. 30 were case-control and 9 were cohort studies; the majority was high quality. 16 studies provided data on individuals of European, 16 of Asian, 6 of South American, and 2 of African descent. In analyses pooling all races, there were dose-response relationships with alcohol and tobacco use, but with substantial heterogeneity (Table). The effect of current smoking vs. never was weaker among Asians than Europeans (European: OR 4.59, 95% CI 3.46-6.10; Asian: OR 2.59, 95% CI 1.99-3.37), with the 95% CI of the estimates not crossing each other's boundaries, indicating statistical significance. Asians also trended toward having weaker effects of long duration cigarette use (>20 years vs never, European: OR 5.00, 95% CI 3.51-7.12; Asian: OR 3.39, 95% CI 1.66-6.94), and of heavy daily cigarette use (>20 per day vs. none, European: OR 4.65, 95% CI 3.12-6.92; Asian: OR 2.70, 95% CI 1.69-4.30). There was no difference of the effect of alcohol on the risk of ESCC by race.Table: Maximally adjusted summary odds ratios: all studiesConclusion: The estimated effects of alcohol and tobacco use on the risk of ESCC from population-based studies are heterogeneous. Contrary to our hypothesis, a weaker effect of tobacco for ESCC was observed among Asians than among Europeans. Differences in the effects of other factors or in the prevalence of tobacco and alcohol use must explain the higher incidence of ESCC among Asians. The study was limited by the small number of studies among individuals of African descent. More studies are needed to understand the cause of the higher incidence of ESCC among African and Asian Americans.