Smokeless tobacco and oral cancer in South Asia: a systematic review with meta-analysis.

Introduction. Smokeless tobacco is considered one of the major risk factors for oral cancer. It is estimated that over 90% of the global smokeless tobacco use burden is in South Asia. This paper aims to systematically review publications reporting epidemiological observational studies published in South Asia from 1984 till 2013. Methods. An electronic search in "Medline" and "ISI Web of Knowledge" yielded 734 publications out of which 21 were included in this review. All publications were assessed for quality using a standard quality assessment tool. Effect estimates (odds ratios (OR)) were abstracted or calculated from the given data. A random effects meta-analysis was performed to assess the risk of oral cancer with the use of different forms of smokeless tobacco. Results and Conclusion. The pooled OR for chewing tobacco and risk of oral cancer was 4.7 [3.1-7.1] and for paan with tobacco and risk of oral cancer was 7.1 [4.5-11.1]. The findings of this study suggest a strong causal link between oral cancer and various forms of smokeless tobacco. Public health policies in affected countries should consider SLT specific cessation programs in addition to campaigns and activities incorporated into smoking cessation programs.