Your stomach is a J-shaped organ in the upper abdomen where digestion begins before food is passed to your intestines. Cancer can arise in any part of the stomach, and is believed to develop slowly over many years.

Stomach cancer -- also referred to as gastric cancer -- is usually preceded by precancerous changes in the stomach lining, although these changes rarely produce symptoms. Because stomach cancer often does not cause symptoms until it is quite advanced, it is not often detected in its earliest stages.

The following factors increase the risk of stomach cancer :

• Infection with the Helicobacter pylori bacterium, which may lead to chronic inflammation of the inner layer of the stomach and possibly precancerous changes; recent research has shown that antibiotic treatment may reduce the risk of stomach cancer -- particularly stomach lymphoma -- in people infected with this bacterium
• A diet high in consumption of smoked and salted foods, such as smoked fish and meat and pickled vegetables; conversely, eating a diet high in fruits and vegetables (particularly those high in beta-carotene and vitamin C can decrease stomach-cancer risk
• High consumption of red meat; studies show that eating red meat more than 13 times per week can double the risk of stomach cancer
• Smoking
• Alcohol abuse
• Previous stomach surgery, such as removal of stomach tissue in patients with ulcers
• Pernicious anemia, a severe inability to produce red blood cells, due to a deficiency of vitamin B12
• Menetrier's disease, a very rare condition associated with large folds in the stomach and low production of stomach acids
• Blood type A (for unknown reasons)
• Family cancer syndromes, such as Lynch syndrome and familial adenomatous polyposis, which increase colorectal-cancer risk and slightly increase stomach-cancer risk
• Family history of stomach cancer
• Stomach polyps (small benign growths that sometimes develop into stomach cancers).

When symptoms of stomach cancer arise, they may include:

• Indigestion and stomach discomfort
• A bloated feeling after eating
• Mild nausea
• Loss of appetite
• Heartburn
• In the more advanced stages of stomach cancer, a patient may experience the following symptoms:
• Blood in the stool
• Vomiting
• Unexplained weight loss
• Stomach pain

These symptoms may also result from more benign illnesses, such as simple indigestion or a stomach virus. However, if you have these symptoms over a long period of time, you should see your doctor.

If your doctor suspects that you may have stomach cancer, you may have a barium x-ray of your upper gastrointestinal system. For this test, you will be asked to drink a liquid containing barium, which makes your stomach easier to see on an x-ray. This test can be performed in a doctor's office or a hospital's radiology department.

The doctor may also look inside your stomach using a gastroscope, a thin, lighted tube that is inserted into your mouth and guided into your stomach (also called upper endoscopy). A camera at the end of the tube enables your doctor to see inside your stomach. Your doctor may take small samples of tissue to examine for cancer cells. (You will receive a spray of anesthetic into your throat or other medication to ensure that you are comfortable during this examination.)

A third, newer technique to diagnose stomach cancer is called endoscopic ultrasound. Similar to gastroscopy, endoscopic ultrasound relies on a thin tube inserted into the mouth and down into the stomach. At the tip of the tube is a small ultrasound probe that bounces sound waves off the stomach walls. This test is useful for estimating how far cancer has spread into the wall of the stomach, to nearby organs, and to nearby lymph nodes -- a process called staging.

Another staging technique is called laparoscopy. This procedure involves minor surgery using a small tube with a camera at the end to look inside your abdomen. Doctors can look at the outside wall of your stomach, examine the lymph nodes, and evaluate the surfaces of other abdominal organs to determine if the cancer has spread to those areas.

In addition to these diagnostic tests, your doctor will take your medical history into account, perform a physical examination, and order laboratory studies such as blood tests.

The choice of treatment for stomach cancer depends on the stage of the disease -- that is, how large the tumor has grown, how deeply it has invaded the layers of the stomach, and whether it has spread to nearby organs, lymph nodes, or other parts of the body

Recent investigations suggest that a three-pronged attack on stomach cancer -- utilizing surgery to remove most of the tumor and chemotherapy and radiation therapy to control cancer spread -- may improve the survival of patients with stomach cancer. This combination approach is expected to become the standard of care for patients with this disease.

Surgery is the most common form of treatment for stomach cancer. If the results of staging indicate that surgery is likely to help you, your doctor may perform one of these operations to remove the cancer :

Removal of the part of the stomach that contains the cancer and parts of other tissues or organs near the tumor (such as the small intestine or esophagus, depending on the location of the tumor)

Removal of the entire stomach and parts of the esophagus, small intestine, and other tissue near the tumor; in this case the esophagus may be connected to the small intestine so that you can continue to eat and swallow

During the surgery, the surgeon will also remove nearby lymph nodes to examine them for cancer cells. Sometimes the spleen (an organ in the upper abdomen that filters blood and removes old blood cells) and part of the pancreas are also removed.

Chemotherapy -- treatment with cancer-killing drugs -- is another option for treating stomach cancer. It can be given to patients whose cancers have invaded the layers of the stomach wall, nearby lymph nodes, and nearby organs. Chemotherapy may be given before surgery (so-called neoadjuvant therapy) -- to shrink the tumor first -- or after surgery (adjuvant therapy), to kill any remaining cancer cells. These approaches are being evaluated in clinical trials.

When given alone or with radiation therapy, chemotherapy is also useful in some patients to relieve stomach-cancer symptoms or to delay cancer recurrence and extend a patient's life, especially in patients whose cancers cannot be completely removed through surgery. 5-fluorouracil and cisplatin are the drugs most commonly used to treat stomach cancer; other drugs (including paclitaxel, docetaxel, and irinotecan) and new combinations of conventional drugs are currently under investigation. Some are given intravenously (through a vein), while others are given intraperitoneally (delivered directly into the abdominal cavity).

Radiation therapy is most commonly used in combination with chemotherapy for the treatment of gastric cancer. New studies reveal that for many patients with gastric cancer, the addition of radiation therapy plus chemotherapy after surgery improves survival compared to surgery alone.