Causes and Risk Factors of Stomach Cancer

Who’s at risk?
What are the symptoms?
How is it diagnosed?
What are the stages?
How is it treated?
How to help prevent stomach cancer

Who’s at risk?

Each year, about 24,000 people in the United States learn they have cancer of the stomach. Stomach cancer, also called gastric cancer, is the fourth most common cancer today, although it is not nearly as common in this country as it was 60 years ago. Dietary changes and the greater use of refrigeration for food storage are credited for the lower incidence of stomach cancer.

Scientists don’t know why some people develop stomach cancer and others don’t. But they do know that some people are more likely than others to develop it. For instance, stomach cancer occurs mostly in men over 40, and is more likely to occur in black people than in white people.

There are other factors that can increase the risk of getting stomach cancer:

Helicobacter pylori (H. pylori). Some studies suggest that a type of bacteria, Helicobacter pylori, which lives in the stomach lining, is a major cause of stomach cancer. It is found in 20% of people age 40 and under and 50% of those who are 60 or over. H. pylori bacteria often cause peptic ulcers. However, stomach ulcers do not appear to raise a person’s risk of developing stomach cancer. People with H. pylori infection have three to eight times greater risk of developing gastric cancer than those not infected, although most never develop stomach cancer.

Diet. A diet high in preserved foods – such as those that are smoked, dried, salted or pickled – that contain nitrates and nitrites are linked to stomach cancer. These substances can be converted inside your stomach into compounds that increase your risk of stomach cancer. Researchers have also found that people who have diets rich in meat, cheese, and whole milk may be at increased risk of developing cancer in both the esophagus and stomach.

Previous stomach surgery. Stomach surgery may result in higher levels of nitrite-producing bacteria and bile in your stomach, which increases the risk of stomach cancer.

Stomach polyps. Polyps are small bumps or larger mushroom-like growths of the lining of the stomach. Most types of polyps (such as hyperplastic polyps or inflammatory polyps) do not increase a person’s risk of stomach cancer, but adenomatous, benign polyps sometimes develop into stomach cancers.

Pernicious anemia. Having chronic vitamin-deficiency anemia can put someone at an increased risk of developing stomach cancer. Pernicious anemia occurs in older adults and is characterized by numbness and tingling in the extremities.

Genetics. Stomach cancers are two to four times more common for immediate family members of those who have had the disease. However, more than 90% of people with stomach cancer have no family members with stomach cancer.

Country of origin. Stomach cancer is more common in some parts of the world – such as Japan, Korea, parts of Eastern Europe, and Latin America – than in the United States. Researchers believe that is because people in these areas eat many foods that are preserved by drying, smoking, salting, or pickling.

Smoking and alcohol abuse. Both of these substances can irritate the lining of the stomach, particularly the upper parts, and increase the risk of developing cancer.

Environmental exposure. Certain dusts and fumes in the workplace have been linked to a higher-than-average risk of stomach cancer.

If caught early, stomach cancer is treatable. However, when the cancer has spread, the outlook isn’t as good. The 5-year survival rate for stomach cancer is 90% when the cancer is detected in its earliest stages. The problem is that often there are no symptoms in the early stages of stomach cancer. When symptoms do occur, they are usually vague or mistaken for other less serious health problems such as a stomach virus or an ulcer that the patient may choose to ignore.

What are the symptoms?

Stomach cancer can cause the following symptoms:

  • Indigestion or a burning sensation (heartburn)
  • Discomfort or pain in the abdomen
  • Nausea and vomiting
  • Diarrhea or constipation
  • Bloated feeling after meals
  • Loss of appetite
  • Weakness and fatigue
  • Bleeding (vomiting blood or having blood in the stool)
  • Black, tarry stools

Any of these problems could be caused by less serious health problems as well. Symptoms should prompt the patient to see the doctor, who may then refer that patient to a gastroenterologist, a doctor who specializes in diagnosing and treating digestive problems.

How is it diagnosed?

To find the cause of your symptoms, the doctor will ask for a medical history, do a physical exam, and may order laboratory tests. They may include one or all of the following exams:

Fecal occult blood test – a check for hidden (occult) blood in the stood. This test is done by placing a small amount of stool on a plastic slide or on a special paper. It may be tested in the doctor’s office or sent to a laboratory.

This test is done because stomach cancer sometimes causes bleeding that cannot be seen. However, noncancerous conditions may also cause bleeding, so having blood in the stool doesn’t mean that you have cancer.

Upper GI series – x-rays of the “GI tract” – the esophagus (which connects your throat and stomach) and stomach. After fasting the night before, the patient drinks a thick, chalky barium liquid. The barium outlines the stomach on the x-rays, helping the doctor find tumors or other abnormal areas. The problem with the x-ray study is that it rarely reveals small, early tumors. The doctor may pump air into the stomach to make such small tumors easier to see.

Endoscopy – an exam of the esophagus and stomach using a thin, lighted tube called an endoscope (also called a gastroscope). Endoscopy is the best diagnostic procedure because it allows the doctor to see the stomach. A local anesthetic is first sprayed into your throat to reduce discomfort and gagging. You may also receive medication to relax you. Your doctor then inserts a thin, flexible tube (endoscope) equipped with a light through your mouth and into your esophagus, stomach, and small intestine. Your doctor will be able to see the upper part of your digestive tract, and remove a small sample (biopsy) of any tissue that appears abnormal for further assessment. The tissue sample is sent to a pathologist who examines it under a microscope to check for cancer cells. A biopsy is the only sure way to know whether cancer cells are present.

If a diagnosis of stomach cancer is made, your doctor may recommend additional tests to determine the extent of the cancer and the best treatment. These tests may include:

Endoscopic ultrasound. Using an endoscope, the doctor can thread a small ultrasound device into the stomach to get a close-up image of it on a computer screen.

Computerized tomography (CT) scan. To see if the cancer has spread to nearby organs, such as the lymph nodes, pancreas, and liver, the doctor may have you undergo a CT scan, which provides an image of your internal organs.

What are the stages?

The four stages of stomach cancer progression are:

Stage 1: Cancer cells are confined to only the inner stomach lining. They are absent from the wall of the stomach or from lymph nodes.

Stages 2: Cancer cells exist in the tissue of the second or third layers of the gastric wall, and may or may not exist in the lymph nodes. Cancer has not spread to other areas.

Stages 3: Cancer cells have spread (metastasized) to other areas adjacent to the stomach.

Stage 4: Cancer cells exist in the lymph nodes and/or distant areas of the body.

How is it treated?

Treatment for stomach cancer depends on the size, location, and extent of the tumor; whether the cancer has spread and, if so, what parts of the body are affected; the patient’s general health; and other factors.

Treatment may include surgery, chemotherapy, and/or radiation therapy. New treatment approaches such as biological therapy and improved ways of using current methods are being studied in clinical trials. A patient may have one form of treatment or a combination of treatments.

Surgery. Surgical removal of the stomach tumor is the most common treatment for stomach cancer. In the operation (called a gastrectomy), the surgeon removes part (subtotal or partial gastrectomy) or all (total gastrectomy) of the stomach, as well as some of the tissue around the stomach. After a subtotal gastrectomy, the surgeon connects the remaining part of the stomach to the esophagus or the small intestine. After a total gastrectomy, he or she connects the esophagus directly to the small intestine. Lymph nodes near the tumor are often removed during surgery so they can be checked for cancer cells. The presence of cancer cells in the lymph nodes tells doctors that the disease may have spread to other parts of the body.

Chemotherapy. In chemotherapy, anticancer drugs are given to kill cancer cells. These drugs work on cancer cells, wherever they are in the body, not just in the stomach. They can be taken orally or are given by injection. Chemotherapy is sometimes used before surgery to shrink the tumor, or after surgery to destroy remaining cancer cells. Doctors are also testing a treatment in which cancer-killing drugs are administered directly into the abdomen.

Chemotherapy is given in cycles: a treatment period followed by a recovery period, then another treatment, and so on.

Radiation therapy. Like surgery, radiation therapy (using x-rays) targets cancer cells in a specific area. Radiation may be used after surgery to destroy remaining cancer cells. The patient usually has radiation treatments 5 days a week for 5 to 6 weeks. Sometimes, this treatment is used in combination with chemotherapy. Researchers are conducting clinical trials to find out whether radiation therapy administered during surgery is helpful.

Biological therapy. This form of therapy, also called immunotherapy, uses the body’s immune system to attack and destroy cancer cells. It may also help a patient recover from some of the side effects of treatment. In clinical trials, doctors are studying biological therapy in combination with other treatments to try to prevent stomach cancer from recurring. In other cases, patients who have low blood cell counts during or after chemotherapy may receive biological therapy (substances made by the body or in a laboratory, such as tumor vaccines) to help restore the blood cell levels.

How can I help prevent stomach cancer?

  • Avoid diets that are high in smoked and pickled foods and salted meats and fish.
  • Eat a diet high in fresh fruits and vegetables. The American Cancer Society recommends that people choose most of the foods they eat from plant sources. This includes fruits, vegetables, breads, cereals, pasta, rice, and beans.
  • Limit or cut out alcohol.

There is also evidence that antibiotics and dietary supplements can thwart precancerous changes that may lead to stomach cancer. Researchers studied 1219 people in the province of Narino, Columbia, in the Andes Mountains, a region with some of the highest stomach cancer rates in the world. Those participating in the study had stomach-lining biopsies that showed precancerous changes. They were given one of the following treatments, or a placebo:

  • Antibiotics alone
  • Beta carotene alone or along with antibiotics
  • Vitamin C alone or along with antibiotics
  • Both vitamin C and beta carotene together, with or without antibiotics

Each treatment increased the likelihood about three- to eight-fold that their next stomach lining biopsy, taken 6 years later, would be normal. Researchers at the Louisiana State University Medical Center, who conducted the study, found that combining two treatments was no more effective than one treatment alone. The study was reported in the Journal of the National Cancer Institute (Dec 6, 2000 issue).

Sources:
National Cancer Institute
The American Cancer Society
US National Library of Medicine