Smoking
Dietary Factors
Helicobacter Pylori Infection
Chemoprevention

Note: Separate PDQ summaries on Stomach (Gastric) Cancer Screening ¹, Gastric Cancer Treatment ², and Levels of Evidence for Cancer Screening and Prevention Studies ³ are also available.

Based on solid evidence, smoking is associated with an increased risk of stomach cancer.[1-3] Based on the 2004 Surgeon General’s report, cigarette smoking is a cause of stomach cancer, with an average relative risk (RR) in former smokers of 1.2 and in current smokers of 1.6.[4] Compared to persistent smokers, the risk of stomach cancer decreases among former smokers with time since cessation. This pattern of observations makes it reasonable to infer that cigarette smoking prevention or cessation would result in a decreased risk of gastric cancer.

• Study Design: Evidence obtained from case-control and cohort studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: A systematic review and meta-analysis showed a 60% increase in gastric cancer in male smokers and a 20% increase in gastric cancer in female smokers compared to nonsmokers.[1]
• External Validity: Good.

Based on fair evidence, excessive salt intake and deficient dietary consumption of fresh fruits and vegetables are associated with an increased risk of gastric cancer. Dietary intake of vitamin C contained in vegetables, fruits, and other foods of plant origin is associated with a reduced risk of gastric cancer. Diets high in whole-grain cereals, carotenoids, allium compounds, and green tea are also associated with a reduced risk of this cancer. However, it is uncertain if changing one's diet to include more vegetables, fruits, and whole grains would reduce the risk of gastric cancer.

Description of the Evidence

• Study Design: Evidence obtained from cohort or case-control studies.
• Internal Validity: Good.
• Consistency: Small number of studies.
• Magnitude of Effects on Health Outcomes: Small, difficult to determine.
• External Validity: Fair (populations vary greatly in their underlying nutritional status).

Based on solid evidence, H. pylori infection is associated with an increased risk of gastric cancer. A meta-analysis of seven studies mostly done in Asia suggests that treatment of H. pylori may reduce gastric cancer risk (from 1.7% to 1.1%), decreasing RR to 0.65 (95% confidence interval, 0.43–0.98).[5] Only two studies assessed gastric cancer incidence, and only two were double-blinded studies. It is unclear how generalizable the results may be to the North American population.

Description of the Evidence

• Study Design: Randomized controlled trials of H. pylori eradication.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: Risk of cancer may be reduced; effect on cancer mortality is not known.
• External Validity: Good.

The evidence is inadequate to determine if dietary or antibiotic interventions will reduce the risk of developing gastric cancer. A chemoprevention trial in China reported a statistically significant reduction of gastric cancer mortality after supplementation with beta carotene, vitamin E, and selenium.

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials.
• Internal Validity: Fair.
• Consistency: Poor.
• Magnitude of Effects on Health Outcomes: Cannot determine.
• External Validity: Fair.

References

1. Ladeiras-Lopes R, Pereira AK, Nogueira A, et al.: Smoking and gastric cancer: systematic review and meta-analysis of cohort studies. Cancer Causes Control 19 (7): 689-701, 2008.  [PUBMED Abstract]
   
   
2. González CA, Pera G, Agudo A, et al.: Smoking and the risk of gastric cancer in the European Prospective Investigation Into Cancer and Nutrition (EPIC). Int J Cancer 107 (4): 629-34, 2003.  [PUBMED Abstract]
   
   
3. La Torre G, Chiaradia G, Gianfagna F, et al.: Smoking status and gastric cancer risk: an updated meta-analysis of case-control studies published in the past ten years. Tumori 95 (1): 13-22, 2009 Jan-Feb.  [PUBMED Abstract]
   
   
4. U.S. Department of Health and Human Services.: The Health Consequences of Smoking: A Report of the Surgeon General. Atlanta, Ga: U.S. Department of Health and Human Services, CDC, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. Available online ⁴. Last accessed October 21, 2009. 
   
   
5. Fuccio L, Zagari RM, Eusebi LH, et al.: Meta-analysis: can Helicobacter pylori eradication treatment reduce the risk for gastric cancer? Ann Intern Med 151 (2): 121-8, 2009.  [PUBMED Abstract]