Incidence and mortality
In 2014, it is estimated that 22,220 Americans will be diagnosed with gastric cancer and 10,990 will die of it. Two-thirds of people diagnosed with gastric cancer are older than 66 years. The disease is much more common in other countries, principally Japan, Central Europe, Scandinavia, Hong Kong, South and Central America, the Soviet Union, China, and Korea. Gastric cancer is a major cause of death worldwide, especially in developing countries.
The major type of gastric cancer is adenocarcinoma (95%). The remaining malignant tumors include lymphomas, sarcomas, carcinoid tumors and other rare types. Distinguishing the common adenocarcinoma from the uncommon lymphoma may sometimes be difficult but is important, due to major differences in staging, treatment, and prognosis. Gastric adenocarcinomas can be further categorized into an intestinal type and a diffuse type. Intestinal-type lesions are frequently ulcerative and occur in the distal stomach more often than the diffuse type. Diffuse-type lesions are associated with a worse prognosis than the intestinal type. The intestinal type tends to be predominant in geographic regions with a high incidence of gastric carcinoma. The decline in the incidence of gastric cancer worldwide is largely due to a decrease in the number of intestinal-type lesions.
The incidence of gastric cancer in the United States has decreased fourfold since 1930 to approximately seven cases per 100,000 people. The reasons for this striking decrease in incidence are not fully understood but are suspected to be related to improved storage of food and changes in diet, such as decreased salt intake. Some populations of Americans are at elevated risk, including elderly patients with atrophic gastritis or pernicious anemia, patients with sporadic gastric adenomas, familial adenomatous polyposis, or hereditary nonpolyposis colon cancer, and immigrant ethnic populations from countries with high rates of gastric carcinoma.[9,10]
Risk factors for gastric cancer include the presence of precursor conditions such as chronic atrophic gastritis and intestinal metaplasia, pernicious anemia, and gastric adenomatous polyps. Genetic and environmental factors include a family history of gastric cancer; low consumption of fruits and vegetables; consumption of salted, smoked, or poorly preserved foods; and cigarette smoking.[11,12] There is consistent evidence that Helicobacter pylori infection of the stomach is strongly associated with both the initiation and promotion of carcinoma of the gastric body and antrum, and of gastric lymphoma.[13,14,15] The International Agency for Research on Cancer (IARC) classifies H. pylori infection as a cause of noncardia gastric carcinoma and low-grade B-cell mucosa-associated lymphatic tissue gastric lymphoma (i.e., a Group 1 human carcinogen).[16,17] Compared with the general population, people with duodenal ulcer disease may have a lower risk of gastric cancer.