title: The association between smokeless tobacco use and pancreatic adenocarcinoma: a systematic review.
abstract: BACKGROUND
  Smokeless tobacco is a possible risk factor for developing pancreatic adenocarcinoma. This systematic review addressed the question: Is there an association between smokeless tobacco use and pancreatic adenocarcinoma diagnosis?
  
  
  METHODS
  Five electronic databases, grey literature, and citations of relevant articles were searched to identify studies. Six researchers double-reviewed records for inclusion in the review. The information extracted from these studies was selected using criteria outlined in the Newcastle-Ottawa Quality Assessment Scale for observational studies. A qualitative synthesis of included studies was performed.
  
  
  RESULTS
  The search of electronic databases resulted in a total of 1747 citations. Eleven studies met the inclusion criteria for this review, including three cohort studies, seven case control studies and one study that pooled data from multiple case-control studies. Studies were heterogeneous in their assessment of exposure intensity and ascertainment of outcomes. Quality of the studies varied. Existing investigations of the association of interest appear to exhibit several types of biases including selection bias, information bias and bias in the analysis.
  
  
  CONCLUSIONS
  The association between smokeless tobacco use and pancreatic adenocarcinoma is inconclusive. More definitive conclusions regarding this relationship await the results of more methodologically rigorous epidemiologic studies.
authors.affiliation: Division of Child & Adolescent Psychiatry, Johns Hopkins University School of Medicine, 550N. Broadway, Ste. 206, Baltimore, MD 21205, United States. Electronic address: mburkey1@jhmi.edu.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Burkey
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 600N. Wolfe St., Baltimore, MD 21287, United States. Electronic address: sfeirman@jhsph.edu.
authors.forename: Shari
authors.initials: S
authors.lastname: Feirman
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, 600N. Wolfe St., Baltimore, MD 21287, United States. Electronic address: han.wingss@gmail.com.
authors.forename: Han
authors.initials: H
authors.lastname: Wang
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, 21 Lower Kent Ridge Rd, Singapore 119077, Singapore. Electronic address: pravidence@gmail.com.
authors.forename: Samuel Ravi
authors.initials: SR
authors.lastname: Choudhury
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, 3400 Civic Boulevard, Philadelphia, PA 19104, United States. Electronic address: surbhi.grover@uphs.upenn.edu.
authors.forename: Surbhi
authors.initials: S
authors.lastname: Grover
authors.affiliation: Division of Surgical Oncology, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, United States. Electronic address: fjohnston@mcw.edu.
authors.forename: Fabian M
authors.initials: FM
authors.lastname: Johnston
mesh_terms: D000230:Adenocarcinoma / Q000209:etiology* / Q000473:pathology; D015331:Cohort Studies; D006801:Humans; D010190:Pancreatic Neoplasms / Q000209:etiology* / Q000473:pathology; D012307:Risk Factors; D014030:Tobacco, Smokeless / Q000009:adverse effects*
keywords: Pancreatic cancer; Pancreatic neoplasms; Smokeless tobacco; Systematic review; Tobacco products