Upper Gastrointestinal System
Stomach, or gastric, cancer usually occurs first in the tissues that line the stomach. Precancerous changes in the stomach lining typically begin years before stomach cancer develops. These changes rarely produce symptoms. Stomach cancer often does not cause symptoms until it is advanced; only about 10 to 20 percent of stomach cancers are detected in their earliest stages.
Although stomach cancer is much less common in the United States now than it has been in the past, the American Cancer Society estimates that 21,000 new cases of stomach cancer were diagnosed in 2010.
Stomach cancer develops most often in people over the age of 65 and is more common in men than in women. It also is much more common in certain regions of Asia, Central and Eastern Europe, and Central and South America than it is in the United States, possibly due to lifestyle and environmental factors.
Types of Stomach Cancer
Most stomach cancers (90 to 95 percent) are adenocarcinomas, which begin in cells that line the stomach. Other less common types of stomach cancer include lymphoma (cancer that begins in cells of the immune system); gastrointestinal stromal tumors (cancer of the muscle or connective tissue of the stomach wall, also known as GIST); and carcinoid tumors (cancer of the hormone-producing cells of the stomach).
Adenocarcinomas can be divided into three types. Each type tends to occur in different groups of people and to have different risk factors.
- Non-cardia stomach cancer. This type of stomach cancer develops from prolonged periods of inflammation and irritation. It is commonly associated with chronic infection with Helicobacter pylori bacteria.
- Diffuse stomach cancer. This type of cancer grows within the stomach wall as individual scattered cells rather than forming a lump or tumor. It can be very difficult to detect using endoscopy, a standard procedure for diagnosing stomach cancer. Diffuse stomach cancer sometimes has a genetic cause.
- Proximal stomach cancer. This type of stomach cancer affects the first part of the stomach and often extends into the area where the stomach and esophagus meet, known as the gastroesophageal junction. Risk factors for this type of cancer include obesity and gastroesophageal reflux disease.
The symptoms of stomach cancer are similar to those of minor conditions such as indigestion or a stomach virus. Individuals who have these symptoms over an extended period of time should consult a doctor. Many people with stomach cancer have no symptoms, or only vague abdominal discomfort. Stomach cancer often reaches an advanced stage before symptoms occur. Symptoms of stomach cancer may include:
- pain or discomfort in the stomach region
- a bloated feeling after eating
- nausea and vomiting
- unexplained weight loss and loss of appetite
- difficulty swallowing or excessive belching with eating
The following factors influence the risk of developing stomach adenocarcinoma:
Infection with Helicobacter Pylori Bacteria
Infection with this type of bacterium may lead to chronic inflammation of the inner layer of the stomach and possibly the development of precancers. Helicobacter pylori infection may also result in certain rare gastric lymphomas, which can be treated by treating the Helicobacter infection with antibiotics.(1)
A diet high in smoked and salted foods, such as smoked fish, meat, and pickled vegetables, has been shown to increase a person's chances of developing stomach cancer. High consumption of red meat also raises this risk. Conversely, eating a diet high in fruits and vegetables (particularly those high in beta-carotene and vitamin C) can decrease this risk. A deficiency in the dietary mineral known as selenium may also increase the risk of gastric cancer.
Stomach cancer is more common among Asians, Pacific Islanders, Hispanics, and African Americans than Caucasians.
Stomach cancer is more common in men than in women.
Stomach cancer is most commonly diagnosed in people over the age of 65.
Other possible risk factors include:
- Smoking and alcohol use
- Previous stomach surgery, such as removal of part of the stomach in individuals with ulcers
- Pernicious anemia, a very rare autoimmune condition in which the stomach no longer produces acid, making it hard to absorb vitamin B12
- Ménétrier disease, which is a very rare condition associated with the growth of large folds in the stomach and low production of stomach acids
- Blood type A (for unknown reasons)
- Family cancer syndromes, such as hereditary nonpolyopsis colorectal cancer (HNPCC), also known as Lynch syndrome, Peutz-Jeghers syndrome, and familial adenomatous polyposis, all of which increase risk of colorectal cancer and slightly increase stomach cancer risk
- Family history of stomach cancer, possibly resulting from E-cadherin mutation
- Family history of breast cancer; people carrying mutations of the inherited genes BRCA1 and BRCA2 may also have a higher rate of stomach cancer.
- Stomach polyps (small benign growths that sometimes develop into stomach cancers)
Gastric Cancer Registry
We have established the Memorial Sloan Kettering Gastric Cancer Registry to better understand the risk factors and epidemiology (characteristics of large numbers of people with the disease) for both young patients and patients with a family history of stomach cancer. This database will help further our understanding of the genetic and environmental causes of stomach cancer, and how they relate. Through this work, Memorial Sloan Kettering investigators have identified at least three subtypes of stomach cancer that have different epidemiology and biology. With a better understanding of the risk factors and detailed characteristics of subsets of stomach cancer, we may eventually be able to tailor therapies specifically to each subtype of disease. Data from the registry also will be used to better guide how stomach cancer is diagnosed, treated, and monitored in patients with the disease, and for monitoring those who may be at an increased risk.
Learn more about the Early Onset and Familial Gastric Cancer Registry.