Epidemiology and etiology of gastric cancer

Gastric cancer remains the second leading cause of cancer-related deaths worldwide. There are regional variations which could be attributed to differences in dietary patterns, and the prevalence of Helicobacter pylori infection. The incidence of gastric cancer is declining worldwide; the reasons for this are incompletely understood. The majority of gastric cancers are adenocarcinomas (intestinal or diffuse type). There is emerging evidence that proximal nondiffuse, diffuse and distal nondiffuse gastric cancer subtypes could have distinct molecular expressions with potential therapeutic implications in the future. The development of gastric cancer is influenced by bacterial, host and environmental factors. Certain genotypes (CagA +, VacA s1) of H. pylori and specific host cytokine polymorphisms (IL-1b, TNF-a) remain important risk factors. Screening for gastric cancer is a community-based practice in Japan; however, the benefits of such screening programs outside Japan where incidence is lower remain unclear. Gastric cancer is diagnosed at an advanced stage in more than 50% of cases in western populations. Advanced gastric cancer carries a poor prognosis with a median survival of 8-10months with systemic treatment.