Stomach cancer

Definition

Stomach cancer (also known as gastric cancer) is a disease in which the cells forming the inner lining of the stomach become abnormal and start to divide uncontrollably, forming a mass or a tumor.

Description

Stomach cancer is the seventh most common cancer in the United States. The American Cancer Society (ACS) estimates that 23,000 new cases of stomach cancer will be diagnosed in 1998 and about 14,000 people will die of the disease. Stomach cancer is much more common in countries such as Japan, Chile, Costa Rica, Hungary, and Poland. It is a leading cause of cancer deaths in many countries in central Asia, central Europe, and central and South America. In the United States, there has been a dramatic drop in the incidence of stomach cancer in the last 50 years. While the exact reason for this decline is not known, it may be related to a decreased use of salting and smoking foods as a means of preserving them and an increased use of refrigeration.

The disease is three times more common in men than in women. It is generally found in people who are 40 years or older. The average age at first diagnosis is 60 years.

The stomach is a J-shaped organ that lies in the abdomen, on the left side. The esophagus (or the food pipe) carries the food from the mouth to the stomach. The stomach produces many digestive juices and acids that mix with the food and aid in the process of digestion. The stomach is divided into five sections. The first three are together referred to as the proximal stomach, and produce acids and digestive juices, such as pepsin. The fourth section of the stomach is where the food is mixed with the gastric juices. The fifth section of the stomach acts as a valve and controls the emptying of the stomach contents into the small intestine. The fourth and the fifth sections together are referred to as the distal stomach. Cancer can develop in any of the five sections of the stomach. The symptoms and the outcomes of the disease may vary depending on the location of the cancer.

Causes & symptoms

While the exact cause for stomach cancer has not been identified, having poor nutritional habits, eating a lot of cured, pickled or smoked foods, eating foods high in starch and low in fiber, smoking, drinking alcohol, and vitamin A deficiency are believed to be risk factors for stomach cancer. Being male, African-American, and over 40 years of age can also increase the risk of developing the disease.

Several studies have identified a bacterium (Helicobacter pylori) that causes stomach ulcers (inflammation in the inner lining of the stomach). Chronic (long-term) infection of the stomach with these bacteria may lead to a particular type of cancer (lymphomas or mucosa-associated lymphoid tissue (MALT)) in the stomach.

People who have had previous stomach surgery for ulcers or other conditions may have a higher likelihood of developing stomach cancers, although this is not certain. Another risk factor is developing polyps, benign growths in the lining of the stomach. Although polyps are not cancerous, some may have the potential to turn cancerous.

While no particular gene for stomach cancer has yet been identified, people with blood relatives who have been diagnosed with stomach cancer are more likely to develop the disease. In addition, people who have inherited disorders such as familial adenomatous polyps (FAP) and Lynch syndrome have an increased risk for stomach cancer. For unknown reasons, stomach cancers occur more frequently in people with the blood group A.

Stomach cancer is a slow-growing cancer and it can be years before it grows very large and produces distinct symptoms. In the early stages of the disease, the patient may only have mild discomfort, indigestion, heartburn, a bloated feeling after eating, and mild nausea. In the advanced stages, a patient will have loss of appetite and resultant weight loss, stomach pains, vomiting, and blood in the stool. Stomach cancer often spreads (metastasizes) to adjoining organs such as the esophagus, adjacent lymph nodes, liver, or colon.

Diagnosis

When a doctor suspects stomach cancer from the symptoms described by the patient, he or she will use several methods to find out if the disease is present. A complete medical history will be taken to check for any risk factors. A thorough physical examination will be conducted to assess all the symptoms. Laboratory tests may be ordered to check for blood in the stool (fecal occult blood test) and anemia (low red blood cell count), which often accompany gastric cancer.

The doctor may perform tests that are more specific, such as a barium x ray of the upper gastrointestinal tract. In this test, the patient is given a chalky, white solution of barium sulfate to drink. This solution coats the esophagus, the stomach, and the small intestine. Air may be pumped into the stomach after the barium solution in order to get a clearer picture. Multiple x rays are taken. The barium coating helps to identify any abnormalities in the lining of the stomach. In another test known as "upper endoscopy," a thin, flexible, lighted tube (endoscope) is passed down the patient's throat. The doctor can view the lining of the esophagus and the stomach through the tube. If any suspicious-looking patches are seen, biopsy forceps can be passed through the tube to collect some of the tissue for microscopic examination. This is known as a biopsy. Sometimes, a small ultrasound probe is attached at the end of the endoscope. This probe sends high frequency sound waves that bounce off the stomach wall. A computer creates an image of the stomach wall by translating the pattern of echoes generated by the reflected sound waves. This procedure is known as an "endoscopic ultrasound."

Treatment

The three standard modes of treatment available for stomach cancer include surgery, radiation therapy, and chemotherapy. While deciding on the patient's treatment plan, the doctor takes into account many factors. The location of the cancer and its stage of advancement are important considerations. In addition, the patient's age, general health status, and personal preferences are also taken into account.

Staging of stomach cancer is based on how deep the growth has penetrated the stomach lining; to what extent (if any) it has invaded surrounding lymph nodes; and to what extent (if any) it has spread to distant parts of the body (metastasized). The more confined the cancer, the better the chance for a cure.

In the early stages of stomach cancer, surgery may be used to remove the cancer. If the cancer is too widespread and cannot be removed by surgery, an attempt will be made to remove blockage and control symptoms such as pain or bleeding. Depending on the location of the cancer, either the proximal portion or the distal part of the stomach may be removed. In a surgical procedure known as total gastrectomy, the entire stomach may be removed. Patients who have had parts of their stomachs removed can lead normal lives. Even when the entire stomach is removed, the patients quickly adjust to a different eating schedule. This involves eating small quantities of food more frequently. High protein foods are generally recommended.

Chemotherapy involves administering anti-cancer drugs either intravenously (through a vein in the arm) or orally (in the form of pills). This can either be used as the primary mode of treatment or after surgery to destroy any cancerous cells that may have migrated to distant sites.

Radiation therapy is often used after surgery to destroy the cancer cells that may not have been completely removed during surgery. Generally, to treat stomach cancer, external beam radiation therapy is used. In this procedure, high-energy rays from a machine that is outside of the body are concentrated on the area of the tumor. In the advanced stages of gastric cancer, radiation therapy is used to ease the symptoms such as pain and bleeding.

Prognosis

The prognosis for patients with early stage cancer depends on the location of the cancer. When cancer is in the proximal part of the stomach, only 10-15% of people survive five years or more, even if they have been diagnosed with early stage cancer. For cancer that is in the distal part of the stomach, if it is detected at an early stage, the outlook is somewhat better. About 50% of the people survive for at least five years or more after initial diagnosis. However, only 20% of the patients are diagnosed at an early stage.

Prevention

By avoiding many of the risk factors associated with the disease, it is possible to prevent many stomach cancers. Excessive amounts of salted, smoked, and pickled foods should be avoided. A diet that is high in fiber and low in fats and starches is believed to lower the risk of several cancers. The American Cancer Society recommends eating at least five servings of fruits and vegetables daily and choosing six servings of food from other plant sources, such as grains, pasta, beans, cereals, and whole grain bread.

Abstaining from tobacco and excessive amounts of alcohol will reduce the risk for many cancers. In countries where stomach cancer is common, such as Japan (where it is five to ten times more common than in the United States), early detection may be the best way to improve the odds of beating this disease.

Key Terms

Anemia

A condition in which iron levels in the blood are low.

Barium x ray (upper GI)

An x-ray test of the upper part of the gastrointestinal (GI) tract (including the esophagus, stomach, and a small portion of the small intestine) after the patient is given a white, chalky barium sulfate solution to drink. This substance coats the upper GI and the x rays reveal any abnormality in the lining of the stomach and the upper GI.

Biopsy

Removal of a tissue sample for examination under the microscope to check for cancer cells.

Chemotherapy

Treatment with drugs that are anti-cancer.

Endoscopic ultrasound

A medical procedure in which sound waves are sent to the stomach wall by an ultrasound probe that is attached to the end of an endoscope. The pattern of echoes that are generated by the reflected sound waves are translated into an image of the stomach wall by a computer.

External radiation therapy

Radiation therapy that focuses high-energy rays from a machine on the area of the tumor.

Familial adenomatous polyps (FAP)

An inherited condition in which hundreds of polyps develop in the colon and rectum.

Fecal occult blood test

A test in which the stool sample is chemically tested for hidden blood.

Lynch syndrome

A genetic condition that predisposes certain families to colon cancer, even when polyps are not present.

Polyp

An abnormal growth that develops on the inside of a hollow organ such as the colon, stomach, or nose.

Radiation therapy

Treatment using high-energy radiation from x-ray machines, cobalt, radium, or other sources.

Total gastrectomy

Surgical removal (excision) of the entire stomach.

Upper endoscopy

A medical procedure in which a thin, lighted, flexible tube (endoscope) is inserted down the patient's throat. Through this tube the doctor can view the lining of the esophagus, stomach, and the upper part of the small intestine.

Further Reading

For Your Information

Books

• Berkow, Robert, et al., eds. Merck Manual of Diagnosis and Therapy, 16th ed. Rahway, NJ: Merck Research Laboratories, 1992.
• Dollinger, Malin. Everyone's Guide to Cancer Therapy. Somerville House Books Limited, 1994.
• Morra, Marion E. Choices. Avon Books, October 1994.
• Murphy, Gerald P. Informed Decisions: The Complete book of Cancer Diagnosis, Treatment and Recovery. American Cancer Society, 1997.

  Organizations

• American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA, 30329. (800) 227-2345. http://www.cancer.org.
• Cancer Research Institute. 681 Fifth Avenue, New York, N.Y., 10022. (800) 992-2623. http://www.cancerresearch.org.
• National Cancer Institute. 9000 Rockville Pike, Building 31, room 10A16, Bethesda, MD, 20892. (800) 422-6237. http://wwwicic.nci.nih.gov.
• National Coalition for Cancer Survivorship. 1010 Wayne Avenue, 7th Floor, Silver Spring, MD 20910-5600. (301) 650-8868.
• Oncolink. University of Pennsylvania Cancer Center. http://cancer.med.upenn.edu.

Gale Encyclopedia of Medicine. Gale Research, 1999.