Incidence
The” incidence of gastric carcinoma in the United States (now about 20,000 cases annually) . has declined dramatically for unknown reasons during the past 30 to 40 years from being the single most common malignant disease to its current rank of approximately seventh. Similar but lesser declines have occurred in Western European and in other Anglo-Saxon countries, but the incidence remains very high in some parts of the world, especially in Japan, certain parts of South America, and Eastern Europe. When population groups emigrate from areas of high incidence to those of low incidence, they tend to attain over several generations the usual rates found in their new environment. An interesting inverse relationship has been noted between the incidence of carcinoma of the stomach and carcinoma of the colon in population groups.