[Epidemiology of Helicobacter pylori infection and gastric cancer]

The incidence of H. pylori infection is steadily declining in developed countries, with a prevalence reduced in younger patients (less than 20 % but remaining still high (over 50 %) in the elderly population. The incidence is stable in developing countries, with a prevalence of 70-80%. Adenocarcinoma is the main type of gastric malignancy. The mechanisms of carcinogenesis and risk factors differ depending on the location proximal (cardia) or distal and the histological type "intestinal" or "diffuse". With approximately 6500 new cases per year and a 80% mortality in France, gastric cancer is relatively frequent and severe. The current dominant etiologic role of H. pylori infection explains the epidemiological changes of recent decades: the decline due to reduced incidence of distal cancers of "intestinal" type whereas "diffuse" and proximal cancer are increasing, the average age of onset of 70 years with a male preponderance associated with the high prevalence of distal intestinal type. The cardia cancer occurs earlier and has a worst prognosis. The main risk factors are chronic gastritis induced by H. pylori, smoking, salty and smoked food, a family history of gastric cancer, Lynch syndrome and hereditary diffuse gastric cancer.