Stomach cancer is a slow-growing cancer that mostly affects older people. Almost all stomach cancers are adenocarcinomas which begin in the mucosa – the cells that form the inner lining of the stomach. A small percentage of stomach cancer are lymphomas, which start in the immune system; gastrointestinal stromal tumors that start in cells in the wall of the stomach; and carcinoid tumors that begin in the stomach's hormone-making cells.
In the United States, the average age at diagnosis is 70. The risk of developing stomach cancer is slightly higher for men than women. Until the late 1930s, stomach cancer was the leading cause of cancer death in the U.S. Its incidence has fallen dramatically, probably because of a reduction in dietary risk factors and the introduction of antibiotics that kill cancer-causing bacteria.
Stomach cancer is still a leading cause of cancer deaths in other countries. It is common in Japan, China, Southern and Eastern Europe, and South and Central America.
A major risk factor for stomach cancer is infection with Helicobacter pylori (H pylori) bacteria. Smoking doubles the risk, and having had previous stomach surgery also increases the risk. Medical conditions such as pernicious anemia, anemia, stomach polyps, infection with the Epstein-Barr virus and immune system deficiencies increase the risk. Eating smoked or salted meats that contain nitrates and nitrites are thought to increase the risk. Other factors that increase the risk for stomach cancer include having type A blood, having a family history of stomach cancer, and working in the coal, metal, and rubber industries.
Eating a diet high in fresh fruits and vegetables and limiting the consumption of cured meats and pickled foods can lower the risk of developing stomach cancer.
Early-stage stomach cancer rarely causes symptoms which is why only about 20 percent of stomach cancers in the U.S. are found early. When symptoms do appear, they can include: loss of appetite, unexplained weight loss, abdominal pain or swelling, a sense of feeling full after a small meal, heartburn, indigestion, nausea and vomiting. These symptoms are usually explained by some other cause but should be checked by a doctor.
Treatment depends on the stage and exact location of the cancer. In general, surgery is the primary treatment for stomach cancer. Chemotherapy, often combined with radiation, is useful in shrinking tumors and relieving symptoms. Late stage stomach cancers are difficult to cure.