Gastric adenocarcinomas are cancers of the gastrointestinal system. There is marked geographic variation in the incidence of gastric adenocarcinoma, with high rates in countries such as Japan and Chile and lower rates in North America. However, the incidence of adenocarcinoma of the gastric cardia is increasing, while distal (antral) cancers are decreasing in incidence. Overall, gastric cancer represents 2.5% of all cancer deaths in the U.S. but is reported by some to be the leading cause of cancer death worldwide (some report hepatocellular carcinoma as number one).
Helicobacter pylori is an important risk factor, but not the only one, and a variety of cofactors are important. These include particular blood group types and a variety of dietary factors (e.g., carcinogens in smoked and pickled foods, lack of antioxidant fruits and vegetables, and diets rich in nitrates and nitrites).
Prior gastric surgery may result in gastric stasis which can also lead to bacterial overgrowth with similar long term effects. Adenomatous polyps are also associated with an increased risk of gastric adenocarcinoma.
Most adenocarcinomas are located in the distal stomach, especially along the lesser curvature of the antrum, which is also where gastric ulcers are most common. Both early and advanced cancers may be polypoid, ulcerating or diffusely infiltrating (like all GI cancers).
Gastric cancers present late, usually with anorexia, nausea and weight loss. Most have distant metastases at the time of presentation and only about 50% are resectable at surgery. Radiation and chemotherapy have limited roles. The prognosis of early vs. advanced cancers differs dramatically with a 5-year survival rate of 90-95% for early cancers and a 10-15% 5-year survival rate for advanced cancers. for this reason, clinical and pathological staging are important in assessing prognosis.