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Association of smokeless tobacco with oral cancer: A review of systematic reviews.

ABSTRACT: INTRODUCTION:Various primary studies and systematic reviews have been conducted to explain the association between smokeless tobacco and oral cancer. This study aims to consolidate and summarize the risk estimates from various systematic reviews with or without meta-analysis to provide the spectrum of estimates on the association between smokeless tobacco use and oral cancer. METHODS:A comprehensive literature search was done on various databases (PubMed, Google Scholar, IndMED, and TOXLINE) by two of the authors independently. Both qualitative and quantitative data extraction and analysis were performed for the included systematic reviews. Range of risk estimates was obtained and analyzed as quantitative findings due to the limitation of an overview of reviews for the pooled estimates. CASP (Critical Appraisals Skills Programme) and AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) tools were used for the quality assessment of the studies included. RESULTS:In total, 12 systematic reviews with or without meta-analysis were included in the review. There was a positive and strong association of Smokeless Tobacco (SLT) use with oral cancer irrespective of gender, region, and type of smokeless tobacco. The risk estimate for the South-East Asia Region (SEAR) ranged 4.44-7.90, for Gutkha it was 8.67, while for Paan it ranged 6.3-7.90 and for overall SLT it ranged 1.36-7.90. Risk estimate for females ranged 5.83-14.56. CONCLUSIONS:The study confirmed the association between SLT use and oral cancer. These findings are of high importance, especially to the South-East Asia Region.

SUBMITTER: Asthana S

PROVIDER: S-EPMC7205108 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Association of smokeless tobacco with oral cancer: A review of systematic reviews.

Asthana Smita S Vohra Parul P Labani Satyanarayana S

Tobacco prevention & cessation 20191008

<h4>Introduction</h4>Various primary studies and systematic reviews have been conducted to explain the association between smokeless tobacco and oral cancer. This study aims to consolidate and summarize the risk estimates from various systematic reviews with or without meta-analysis to provide the spectrum of estimates on the association between smokeless tobacco use and oral cancer.<h4>Methods</h4>A comprehensive literature search was done on various databases (PubMed, Google Scholar, IndMED, a ...[more]

PMID: 32411897

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Project description:AimThis systematic review and meta-analysis aimed to critically appraised data from comparable studies leading to quantitative assessment of any independent association between use of oral smokeless tobacco in any form, of betel quid without tobacco and of areca nut with incidence of oral cancer in South Asia and the Pacific.MethodsStudies (case control and/or cohort) were identified by searching Pub Med, CINAHL and Cochrane databases through June 2013 using the keywords oral cancer: chewing tobacco; smokeless tobacco; betel quid; betel quid without tobacco; areca nut; Asia, the Pacific and the reference lists of retrieved articles. A random effects model was used to compute adjusted summary OR(RE) for the main effect of these habits along with their corresponding 95% confidence intervals. To quantify the impact of between-study heterogeneity on adjusted main-effect summary OR(RE), Higgins' H and I2 statistics along with their 95% uncertainty intervals were used. Funnel plots and Egger's test were used to evaluate publication bias.ResultsMeta-analysis of fifteen case-control studies (4,553 cases; 8,632 controls) and four cohort studies (15,342) which met our inclusion criteria showed that chewing tobacco is significantly and independently associated with an increased risk of squamous-cell carcinoma of the oral cavity (adjusted main-effect summary for case- control studies OR(RE) = 7.46; 95% CI = 5.86-9.50, P<0.001), (adjusted main-effect summary for cohort studies RR = 5.48; 95% CI = 2.56-11.71, P<0.001). Furthermore, meta-analysis of fifteen case control studies (4,648 cases; 7,847 controls) has shown betel quid without tobacco to have an independent positive association with oral cancer, with OR = 2.82 (95% CI = 2.35-3.40, P<0.001). This is presumably due to the carcinogenicity of areca nut. There was no significant publication bias.ConclusionThere is convincing evidence that smokeless (aka chewing) tobacco, often used as a component of betel quid, and betel quid without tobacco, are both strong and independent risk factors for oral cancer in these populations. However, studies with better separation of the types of tobacco and the ways in which it is used, and studies with sufficient power to quantify dose-response relationships are still needed.

Project description:IntroductionSmokeless tobacco (ST) was consumed by 356 million people globally in 2017. Recent evidence shows that ST consumption is responsible for an estimated 652 494 all-cause deaths across the globe annually. The WHO Framework Convention on Tobacco Control (FCTC) was negotiated in 2003 and ratified in 2005 to implement effective tobacco control measures. While the policy measures enacted through various tobacco control laws have been effective in reducing the incidence and prevalence of smoking, the impact of ST-related policies (within WHO FCTC and beyond) on ST use is under-researched and not collated.Methods and analysisA systematic review will be conducted to collate all available ST-related policies implemented across various countries and assess their impact on ST use. The following databases will be searched: Medline, EMBASE, PsycINFO, Cumulative Index to Nursing and Allied Health Literature, Scopus, EconLit, ISI Web of Science, Cochrane Library (CENTRAL), African Index Medicus, LILACS, Scientific Electronic Library Online, Index Medicus for the Eastern Mediterranean Region, Index Medicus for South-East Asia Region, Western Pacific Region Index Medicus and WHO Library Database, as well as Google search engine and country-specific government websites. All ST-related policy documents (FCTC and non-FCTC) will be included. Results will be limited to literature published since 2005 in English and regional languages (Bengali, Hindi and Urdu). Two reviewers will independently employ two-stage screening to determine inclusion. The Effective Public Health Practice Project's 'Quality Assessment Tool for Quantitative Studies' will be used to record ratings of quality and risk of bias among studies selected for inclusion. Data will be extracted using a standardised form. Meta-analysis and narrative synthesis will be used.Ethics and disseminationPermission for ethics exemption of the review was obtained from the Centre for Chronic Disease Control's Institutional Ethics Committee, India (CCDC_IEC_06_2020; dated 16 April 2020). The results will be disseminated through publications in a peer-reviewed journal and will be presented in national and international conferences.Prospero registration numberCRD42020191946.

Project description:To evaluate the toxicity of smokeless tobacco products (STPs) on oral bacteria, seven smokeless tobacco aqueous extracts (STAEs) from major brands of STPs and three tobacco-specific N-nitrosamines (TSNAs) were used in a growth and viability test against 38 oral bacterial species or subspecies. All seven STAEs showed concentration-dependent effects on the growth and viability of tested oral bacteria under anaerobic culture conditions, although there were strain-to-strain variations. In the presence of 1 mg/ml STAEs, the growth of 4 strains decreased over 0.32-2.14 log10 fold, while 14 strains demonstrated enhanced growth of 0.3-1.76 log10 fold, and the growth of 21 strains was not significantly affected. In the presence of 10 mg/ml STAEs, the growth of 17 strains was inhibited 0.3-2.11 log10 fold, 18 strains showed enhanced growth of 0.3-0.97 log10 fold, and 4 strains were not significantly affected. In the presence of 50 mg/ml STAEs, the growth of 32 strains was inhibited 0.3-2.96 log10 fold, 8 strains showed enhanced growth of 0.3-1.0 log10 fold, and 2 strains were not significantly affected. All seven STAEs could promote the growth of 4 bacterial strains, including Eubacterium nodatum, Peptostreptococcus micros, Streptococcus anginosus, and Streptococcus constellatus. Exposure to STAEs modulated the viability of some bacterial strains, with 21.1-66.5% decrease for 4 strains at 1 mg/ml, 20.3-85.7% decrease for 10 strains at 10 mg/ml, 20.0-93.3% decrease for 27 strains at 50 mg/ml, and no significant effect for 11 strains at up to 50 mg/ml. STAEs from snuffs inhibited more tested bacterial strains than those from snus indicating that the snuffs may be more toxic to the oral bacteria than snus. For TSNAs, cell growth and viability of 34 tested strains were not significantly affected at up to 100 ?g/ml; while the growth of P. micros was enhanced 0.31-0.54 log10 fold; the growth of Veillonella parvula was repressed 0.33-0.36 log10 fold; and the cell viabilities of 2 strains decreased 56.6-69.9%. The results demonstrate that STAEs affected the growth of some types of oral bacteria, which may affect the healthy ecological balance of oral bacteria in humans. On the other hand, TSNAs did not significantly affect the growth of the oral bacteria.

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Association of smokeless tobacco with oral cancer: A review of systematic reviews.

Publications

Association of smokeless tobacco with oral cancer: A review of systematic reviews.

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