Smokeless Tobacco and Oral Cancer in the Middle East and North Africa: a Systematic Review and Meta-Analysis
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Tobacco Induced Diseases Research Paper Smokeless tobacco and oral cancer in the Middle East and North Africa: A systematic review and meta-analysis Mir Faeq Ali Quadri1, Santosh Kumar Tadakamadla2,3, Tenny John1 ABSTRACT INTRODUCTION Cancer of the oral cavity is regarded lethal with a fairly low mean 5-year survival rate. The current systematic review and meta-analysis is the first AFFILIATION of its kind to examine, if the evidence from the Middle East and North African 1 Faculty of Dentistry, Jazan University, Jazan, Saudi Arabia region indicates an association between oral cancer and tobacco; and evaluates 2 School of Dentistry and Oral the quality of the evidence that portrays this relationship. Health, Griffith University, Southport, Australia METHODS A search for articles was carried out in October 2017 and then cross- 3 Menzies Health Institute checked at the end of June 2018 using Medline, Web of Science, CINAHL, and Queensland (MHIQ), Cochrane databases. Retrieved articles were later subjected to eligibility criteria. Southport, Australia The search was not limited to any particular research design adopted by the CORRESPONDENCE TO investigators. However, dissertations, theses and opinion-based reviews generated Mir Faeq Ali Quadri. College of Dentistry, Jazan University, from the search were excluded during the screening of titles and abstracts. Quality PO Box-114, Jazan 4514, of included studies was determined objectively (Newcastle Ottawa Scale) and Saudi Arabia. E-mail: dr.faeq. [email protected] subjectively. Revman (Version 5.3) was used for conducting the meta-analysis. ORCID ID: https://orcid. RESULTS Six studies satisfied the selection criteria of the current review. The New org/0000-0001-6349-6136 Castle Ottawa evaluation scale suggested that the three cross-sectional studies and KEYWORDS the three case-control studies included in the current review were of relatively systematic review, meta- low to moderate quality. All included studies explored the association of only one analysis, smokeless tobacco, oral cancer, shammah form of smokeless tobacco, i.e. shammah. Three case-control studies revealed a pooled estimate odds ratio of 38.74 (95% CI: 19.50–76.96), indicating that the Received: 5 May 2019 Revised: 3 June 2019 odds for the occurrence of oral cancer among shammah users were nearly 39 Accepted: 26 June 2019 times higher compared to the non-users. CONCLUSIONS Shammah is a potential risk factor for oral cancer; thus, it is necessary that public health practitioners design and implement effective strategies to prevent the abuse of shammah. Tob. Induc. Dis. 2019;17(July):56 https://doi.org/10.18332/tid/110259 INTRODUCTION the disease and its associated risk factors, but region- The global annual incidence rate of 354864 new cases specific studies on oral cancer (OC), as suggested in of oral cancer (oral cavity and lip cancer) makes it one the first meeting of the Global Oral Cancer Forum, of the most common non-communicable diseases1. are also equally important6. The existing disparity Some epidemiological studies have considered it of disease prevalence and associated risk factors to be the sixth most prevalent cancer and one of among populations residing in different regions of the foremost contributors towards mortality2,3. The the globe could be explained in a better way through reputation of being lethal is also demonstrated by its region-specific studies, which add more weight to the low mean 5-year survival rate, with many of the deaths findings as they consider and control for common from the developing nations2,4,5. Such nationwide contributing factors like genetics, habits, and lifestyle. datasets provide good insight on the prevalence of Some regions like Europe, Oceania and North America Published by European Publishing on behalf of the International Society for the Prevention of Tobacco Induced Diseases (ISPTID). © 2019 Quadri M.F.A. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License. (https://creativecommons.org/licenses/by/4.0/) 1 Tobacco Induced Diseases Research Paper have population-based cancer registries, which cover portrays this relationship. a large part of their residents, while the same is yet to be completely followed by South-East Asia and METHODS Middle Eastern regions7. Thus, region-specific studies Permission and registration will enhance the provision of comparative data from The framework of this review was based on the representative samples. guidelines provided by the Preferred Reporting One such region with a history of confined culture Items for Systematic Reviews and Meta-Analyses and heritage is the Middle East and North Africa (PRISMA)22. The protocol was registered with the (MENA). According to the World Bank, there are International Prospective Register of Systematic 19 countries in the MENA region with populations reviews and was assigned the following identification similar in many characteristics8. The countries that code: PROSPERO–CRD–42018093137. belong to the MENA region are: Algeria, Bahrain, Djibouti, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Eligibility criteria Libya, Morocco, Oman, Qatar, Saudi Arabia, Syria, All publications in English language journals Tunisia, United Arab Emirates, West Bank and Gaza demonstrating the relationship between oral cancer Strip, and Yemen. Reports have predicted an increased and smokeless tobacco in the MENA region were oral cancer burden in the MENA region, attributed included. The search of published articles was not to population growth, ageing population, diagnostic limited to any particular research design adopted by methods, and most importantly due to excessive the investigators. However, dissertations, theses and substance abuse9,10. opinion-based reviews generated from the search The World Health Organization on its website were excluded during the screening of the titles and affirms that the heavy use of tobacco is one of the abstracts. Research studies conducted on human main contributing factors towards the growing participants residing in the MENA region, irrespective incidence of oral cancer9. Depending on the method of of sex, age and socioeconomic status were included consumption, tobacco is broadly divided into smoked in this review. Studies performed on expatriate tobacco and smokeless tobacco. Smokeless tobacco populations residing in the MENA region were not is not burnt but is most often snuffed, chewed, or included as the habit of tobacco use as well as the dipped11. However, there are more than twenty- type of tobacco consumed may vary between the local eight different varieties of smokeless tobacco being residents and the expatriates23. consumed globally12, and in the MENA region it is known through different names such as: shammah, Exposure and outcome toombak, maras, nass and neffa13. Consumers, who Exposure comprised any form of smokeless tobacco are reportedly adult males14-16, place the orally used reported to be consumed, irrespective of the method smokeless tobacco either in their buccal mucosa, labial (chewing, dipping etc.) of consumption, duration mucosa or under the tongue, and then suck (dipped) of the habit, or frequency. The outcome was or chew it on a timely basis11. histopathologically confirmed cancer cases of the Smokeless tobacco is equally addictive as smoked oral cavity. Premalignant lesions and any other non- tobacco17-19, and its association with oral cancer confirmed oral lesions were not considered as only is demonstrated by systematic reviews from the a small percentage of them progress into malignant Asia Pacific region20, Europe, and North America21. cases on detection24,25. The PICO/PECO question However, there is no systematic review from the for this review was: ‘Is oral cancer (Outcome) more MENA region on this relationship. We postulate that common in smokeless tobacco users (Exposure) in the studies conducted in the MENA region provided comparison to non-users (Comparator) among the low quality evidence to support this relationship. residents of the MENA region (Participants)?’. Thus, the objectives of this study are: 1) examine if the evidence from the MENA region indicates Information sources and search strategy an association between oral cancer and smokeless Search for articles was carried out in October 2017 tobacco, and 2) evaluate the quality of evidence that and then updated at the end of June 2018 using Tob. Induc. Dis. 2019;17(July):56 https://doi.org/10.18332/tid/110259 2 Tobacco Induced Diseases Research Paper Medline, Web of Science, CINAHL, and Cochrane for that particular item. The subjective assessment to databases. Multiple searches were performed using report on the quality of the published studies involved various combinations of keywords including the critical appraisal of articles by one author (MFAQ) and Medical Subject Heading terms (Table 1). Reference a subsequent cross-check by another author (SKT) lists of the included studies were also screened for using criteria proposed by Hermont et al.26. relevant articles. Quantitative assessment Study selection and data extraction Meta-analysis was conducted for the three case- Reviewers (SKT and MFAQ) independently control studies that assessed the association between performed article searches using search strings given shammah and oral cancer using Revman (Version in Table 1. No discrepancies in the list of articles were 5.3)27. Odds ratio was the summary estimate in all the detected after removing the duplicates. The