Stomach cancers

Also known as: Gastric cancer, esophageal cancer, adenocarcinoma

Related conditions:Peptic ulcers, lymphoma, gastritis, pernicious anemia, Helicobacter pylori infection, adenomatous polyps

Definition:Stomach cancers are malignant tumors of the stomach, about 90–95 percent of which are adenocarcinomas that develop from the glandular epithelial cells of the innermost lining of the stomach (mucosa). Others types include stomach lymphoma (about 4 percent of stomach cancers), carcinoid tumors of the hormone-producing cells (3 percent), and rare gastrointestinal stromal tumors (GISTs) of the interstitial cells of Cajal (part of the autonomic nervous system controlling stomach muscle movement).

Risk factors: Long-term infection with the bacterium Helicobacter pylori causes inflammation that can cause precancerous changes in the stomach lining. Age, gender, and ethnicity are also risk factors; most people who develop stomach cancer are older than the age of fifty, men develop stomach cancers at double the rate of women in the United States, and Caucasians are at less risk than African Americans, Hispanics, and Asians. Familial cancer syndromes, inherited disorders, and having a parent or sibling with the disease increase the risk of stomach cancer. Pernicious anemia (inability to absorb vitamin B¹²), obesity, and having type A blood are also risk factors.

Rates of stomach cancer, especially at the esophagus-stomach junction, are higher in cigarette smokers. A diet high in foods preserved by smoking, salting, or pickling; large amounts of red meat, particularly if barbecued or well-done; and foods that contain nitrites and nitrates (that can form N-nitroso carcinogens), such as bacon, ham, hot dogs, and processed meats, increase the risk.

People with part of their stomach and pyloric valve removed as a treatment for peptic ulcers also are at increased risk. After stomach surgery, bile or pancreatic juices can accumulate, causing gastritis. The amount of protective stomach acid also decreases while nitrite-producing bacteria may increase, leading to stomach cancer.

Small growths (polyps) in the stomach lining, especially adenomatous polyps, may also be precancerous.

Etiology and the disease process: Most stomach cancers start in the innermost mucosal layer of the stomach, where stomach acid and digestive enzymes are made, and develop slowly over many years. Before a true cancer develops, precancerous changes occur in the lining of the stomach, such as atrophic gastritis, a condition in which the acid-producing glands are slowly destroyed. Low acid levels prevent cancer-causing toxins from being properly broken down or flushed out of the stomach. Stomach cancers can spread in different ways: through the wall of the stomach to invade nearby organs; through the bloodstream to the lungs, bones, and ovaries; or to the lymph vessels and lymph nodes slowly or aggressively. Carcinoid tumors grow less quickly and metastasize less frequently.

Incidence: In the United States, about 9.7 men per one hundred thousand and 4.8 women per one hundred thousand are diagnosed with stomach cancer each year, with about 22,220 cases and 10,990 deaths estimated for 2014 according to the American Cancer Society. Hispanics, Native Americans, Asian Americans, and African Americans are roughly twice as likely to develop gastric cancer as whites. The incidence of stomach cancer is in decline in the United States and Western Europe, probably because of increasingly better, more balanced diets; the frequent use of antibiotics that reduce H. pylori and childhood infections; and refrigeration, which reduces nitrate-producing bacteria in food.

The disease remains a serious problem in many parts of the world, however, with higher rates in developing countries and and certain other countries. Infection with H. pylori and traditional diets are thought to influence this trend, though some geographic factors are not fully uinderstood. Areas where stomach cancer is more common include Japan, Korea, Brazil, and Iceland.

Symptoms: Stomach cancer rarely produces initial symptoms and is usually detected in advanced stages. Depending on their location in the stomach, cancers may have different symptoms and outcomes. One early sign is microscopic internal bleeding, which is detected only by tests that check the stool for blood. Other early symptoms are heartburn and abdominal pain, which can be mistaken for other common problems such as peptic ulcers.

Advanced cases can produce discomfort in the upper or middle region of the abdomen that may not be relieved by food or antacids; abdominal discomfort aggravated by eating; chronic abdominal pain; swelling; black, tarry stools; indigestion; nausea; vomiting blood; vomiting after meals; weakness and fatigue; unintended weight loss; and a full feeling after meals, even when eating less than normal.

Screening and diagnosis: Early diagnosis of stomach cancer is hindered by its initial vague symptoms; the disease can easily be mistaken for less serious problems such as a stomach virus or heartburn. Diagnosis includes a complete medical history and physical examination, barium X rays of the gastrointestinal tract with fluoroscopy showing changes, gastroscopy with fiber-optic endoscopy that helps rule out other diffuse gastric mucosal abnormalities, photography with a fiber-optic endoscope that provides a permanent record of gastric lesions, and biopsy for microscopic examination to confirm cancer when abnormal cells are discovered.

Screening of serum sample glycoprotein antigens produced by cancer cells reveals undetected cancer and monitors established cancer.

Polymerase chain reaction (PCR) kits, which amplify and detect altered deoxyribonucleic acid (DNA) base sequences in minute samples of cells, facilitate the diagnosis of cancer types that are difficult to categorize by conventional pathology.

Treatment and therapy: Stomach cancer is treatable if caught early. Pain is often relieved by food or acid-buffering medications in the early stages. The kind of treatment for stomach cancer depends on the location of the cancer, how advanced it is, and the patient’s overall health and personal preferences. The most common treatment for stomach cancer is surgery. Depending on the extent of the cancer, the doctor may perform a gastrectomy to remove part (subtotal, or partial, gastrectomy) or all of the stomach (total gastrectomy), as well as surrounding tissue and lymph nodes. After subtotal gastrectomy, the remaining part of the stomach is connected to the esophagus and small intestine. For total gastrectomy, the esophagus is connected directly to the small intestine.

Prognosis and treatment for stomach lymphoma depend on the extent of aggressiveness. Individuals who have H. pylori-associated gastric lymphomas may be cured by antibiotic therapy that eliminates the bacteria. In some advanced cases, a laser beam directed through an endoscope can vaporize most of the tumor without an operation.

Radiation therapy, chemotherapy, or a combination of both is used to completely destroy all remaining cancer cells after surgery.

Prognosis, prevention, and outcomes: The prognosis for stomach cancer depends on the stage of the disease at the time of diagnosis and is dim if the cancer has grown deeper into layers of the stomach or has spread to the lymph nodes. The American Cancer Society's estimates of five-year survival rates for stomach cancer range from about 71 percent for diagnosis in Stage IA to 4 percent when diagnosed in Stage IV.

To help prevent stomach cancer, people should eat plenty of fresh fruits and vegetables with antioxidant vitamins and polyphenols, especially those high in vitamin C and beta-carotene and deeply colored, such as mango, cantaloupe, strawberries, carrots, tomatoes, red bell peppers, Swiss chard, bok choy, spinach, acorn and butternut squash, sweet potatoes, broccoli, brussels sprouts, and cauliflower. A preventative diet should avoid nitrites and nitrates in processed and cured meats; consume more fish or poultry instead of red meat; limit smoked, pickled, and heavily salted foods. Smoking should be avoided. Physical exercise and maintaining a healthy body weight are also thought to contribute to cancer prevention.

Bibliography

Beers, Mark H., et al., eds. The Merck Manual of Medical Information: Second Home Edition. 2003. Whitehouse Station: Merck Research Laboratories, 2008. Print.

King, R. J. B., and Mike W. Robins. Cancer Biology. 3rd ed. New York: Prentice Hall, 2006. Print.

Shah, Manish A. Dx/Rx: Upper Gastrointestinal Malignancies: Cancers of the Stomach and Esophagus. Sudbury: Jones, 2006. Print.

"Stomach Cancer." Cancer.net. American Society of Clinical Oncology, 2014. Web. 18 Dec. 2014.

"Stomach Cancer." Cancer.org. American Cancer Society, 5 Nov. 2014. Web. 18 Dec. 2014.

"Stomach Cancer." Mayo Clinic. Mayo Foundation for Medical Education and Research, 26 Apr. 2013. Web. 18 Dec. 2014.