Systematic review with meta-analysis: Race-specific effects of alcohol and tobacco on the risk of oesophageal squamous cell carcinoma

Background Oesophageal squamous cell carcinoma (OSCC) is associated with alcohol use, tobacco use and African or Asian descent. However, little is known about how racial background modifies the effects of alcohol or tobacco. Aim To investigate how racial and geographical background modifies the effect of alcohol and tobacco on OSCC via a systematic review and meta-analysis of published literature. Methods We performed a literature search in multiple online databases regardless of language. Eligible studies were population-based assessments of the effect of tobacco and/or alcohol on the risk of OSCC allowing stratification by race. The quality of studies was assessed by the Newcastle-Ottawa Scale. Meta-analyses were performed to estimate summary effects using random effect models. Results Systematic review identified 9668 unique citations of which 34 were eligible. The majority were of high quality. The effect of current smoking vs. never-smoking was weaker among Asians than among Europeans [European: odds ratio (OR) = 4.21, 95% confidence interval (CI) 3.13, 5.66; Asian: OR = 2.31, 95% CI 1.78, 2.99], with the 95% CIs not crossing, indicating statistical significance. Asians also trended towards weaker effects of long-duration cigarette use and of heavy daily cigarette use. There was no difference in the effect of alcohol on OSCC risk by race. Conclusions Contrary to our hypothesis, a weaker effect of tobacco for OSCC was observed among Asians than among Europeans. Differences in other factors must explain the higher incidence of OSCC among Asians. More studies are needed to understand the cause of the disparate incidence of OSCC between races.