Epidemiology of gastric cancer: an evaluation of available evidence.

Despite a dramatic reduction in incidence and mortality rates, gastric cancer (GC) is still one of the most common malignant neoplasias worldwide. Surgical and medical treatments have not substantially improved during the last decades, and large-scale early diagnosis programs have proven feasible in only one high-risk country, Japan. A large number of studies have indicated that salted, smoked, pickled, and preserved foods (rich in salt, nitrite, and preformed N-nitroso compounds) are associated with an increased risk of GC. In contrast, strong evidence has been provided that high consumption of fresh fruit and raw vegetables and a high intake of antioxidants are associated with a reduced risk of GC. Domestic refrigeration and reduced salt consumption are considered to play a role in explaining the decreasing temporal trend and the geographical patterns of GC. Familial factors have been suspected to play a role in GC susceptibility, and recently germ line mutations in the E-cadherin gene were identified in a few families. Evidence of a positive association between Helicobacter pylori infection and GC risk has been provided by most prospective studies that overall suggest a two- to threefold increase in risk. Randomized intervention studies on H. pylori eradication and its effects on GC predisposing conditions (atrophic gastritis and intestinal metaplasia) are in progress and represent a priority for epidemiological research in view of the potential preventive applications. Overall, it is evident that several factors (including diet, individual susceptibility and H. pylori infection) interact in a complex multifactorial process, leading over a long period of time to GC.