title: Cytotoxin-Associated Gene A-Negative Strains of Helicobacter pylori as a Potential Risk Factor of Pancreatic Cancer: A Meta-Analysis Based on Nested Case-Control Studies.
abstract: OBJECTIVE
  Risk of pancreatic cancer between Helicobacter pylori infected and noninfected persons is controversial, and therefore a meta-analysis was performed.
  
  
  METHODS
  PubMed was searched up to September 2014. Only population-based nested case-control studies comparing the serological prevalence of Helicobacter pylori between pancreatic cancer cases and cancer-free controls were eligible. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for pancreatic cancer risk between Helicobacter pylori infected and noninfected persons were estimated.
  
  
  RESULTS
  Five eligible nested case-control studies were included, with 1446 pancreatic cancer cases and 2235 cancer-free controls. On the whole, the proportion of pancreatic cancer cases among those infected with Helicobacter pylori was not significant different from those noninfected (OR, 0.99; 95% CI, 0.65-1.50; P = 0.96). Likewise, seropositivity of cytotoxin-associated gene A (CagA) showed nonsignificant association with pancreatic cancer (OR, 0.92; 95% CI, 0.65-1.30; P = 0.63). The CagA-positive virulent strains of Helicobacter pylori did not increase the risk of pancreatic cancer (OR, 0.97; 95% CI, 0.50-1.89; P = 0.93). However, CagA-negative nonvirulent strains of Helicobacter pylori had a significant increased risk for pancreatic cancer (OR, 1.47; 95% CI, 1.11-1.96; P = 0.008).
  
  
  CONCLUSIONS
  The CagA-negative non-virulent strains of Helicobacter pylori may be a potential risk factor of pancreatic cancer. High-quality prospective large-scaled studies are required for more conclusive results.
authors.affiliation: From the *Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, China; †Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), Heidelberg, Germany; and ‡Nursing Section, Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Xin-Zu
authors.initials: XZ
authors.lastname: Chen
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Hai-Ning
authors.initials: HN
authors.lastname: Chen
authors.forename: Jian-Kun
authors.initials: JK
authors.lastname: Hu
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D016022:Case-Control Studies; D016481:Helicobacter Infections / Q000150:complications* / Q000382:microbiology; D016480:Helicobacter pylori / Q000378:metabolism* / Q000502:physiology; D054884:Host-Pathogen Interactions; D006801:Humans; D016017:Odds Ratio; D010190:Pancreatic Neoplasms / Q000150:complications* / Q000382:microbiology; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C080866:cagA protein, Helicobacter pylori