What Are the Causes Gastric Cancer?

In general, cancer begins when a genetic mutation (change in certain genes) turns normal, healthy cells into abnormal cells. Healthy cells grow and multiply at a set rate and eventually die at a set time. Abnormal cells grow and multiply out of control, and they do not die. The abnormal cells clump together to create a mass (tumor). These cancer cells can invade nearby tissues. They can also separate from the initial tumor and travel to other parts of the body (metastasize).

Certain changes in our DNA (a chemical that carries the instructions for almost everything our cells do) can make normal cells cancerous. Some genetic diseases (including hereditary diffuse gastric cancer, an inherited stomach cancer that tends to affect a lot of the stomach rather than one part of the stomach, and hereditary non-polyposis colorectal cancer, which increases the risk of colorectal and other cancers) seem to play a role in the development of a small percentage of gastric cancer cases.

In most cases, however, mutations (changes) in the genes that control the growth and division of cells and are related to gastric cancer occur after you are born and are not inherited from your parents. These mutations may happen because you have been exposed to cancer-causing chemicals (including those in tobacco smoke) in the environment or your diet. They can also happen for no apparent reason.

Scientists have identified the following factors that can damage DNA in stomach cells, making those cells become cancerous:

• Helicobacter pylori (H. pylori) infection - H. pylori bacteria can turn certain chemicals in some kinds of food into cancer-causing chemicals that cause mutations in the DNA of the stomach lining cells. More than half the world’s population is infected with this bacterium. Scientists believe that more than 50 percent of all gastric cancers are caused by this infection, but most people with H. pylori in their stomachs never develop gastric cancer.
• Precancerous conditions - Scientists believe that some changes in the stomach lining are precancerous. For example, H. pylori can destroy the stomach glands, leading to a condition called atrophic gastritis, which can turn into gastric cancer. Another condition, intestinal metaplasia, can also progress to gastric cancer. People with intestinal metaplasia have cells that are similar to the cells that usually line the intestine.
• Diet - Nitrates and nitrites are nitrogen-based chemicals that are added to cured meats, such as ham, bacon, hot dogs, and deli meats. These chemicals have been associated with an increased risk of stomach cancer. Pickled, salted, and smoked foods also contain large amounts of nitrates and nitrites. Pickling, salting, and smoking used to be used to preserve foods before refrigeration became widely available. Several countries where many people eat a lot of salted meat and fish and pickled vegetables, such as Japan and Korea, have high rates of gastric cancer.
• Tobacco and alcohol use - Tobacco can irritate the stomach lining, which can lead to gastric cancer. Alcohol also seems to play a role in causing stomach cancer, although scientists do not understand its role yet.
  

Risk Factors for Gastric Cancer

Doctors and researchers believe that certain factors, known as risk factors, increase a person’s chances of getting gastric cancer. However, not everyone with a risk factor will develop gastric cancer and people without any risk factors can develop the disease.

Risk factors for gastric cancer include:

• Age - The risk of developing gastric cancer increases significantly after age 50. Most people diagnosed with stomach cancer are in their 60s or older.
• Blood type A - A person’s blood type is based on certain substances that are normally found on red blood cells. People with type A blood have a slightly higher risk of gastric cancer.
• Diet - Eating a lot of smoked foods, salted fish and meat, processed meats, red meat, and pickled vegetables can increase your risk of gastric cancer. These foods often have nitrates and nitrites. Researchers have shown that certain bacteria, including H. pylori, can convert these chemicals into compounds that cause stomach cancer in animals. Eating fresh fruits and vegetables that contain antioxidant vitamins (such as vitamins A and C) seems to lower the risk of gastric cancer because these vitamins can block substances that damage cell DNA.
• Ethnicity - Gastric cancer is more common in Asians/Pacific Islanders, Hispanic Americans, and African Americans than in non-Hispanic whites.
• Family history - Gastric cancer is sometimes caused by an inherited condition, such as:
  
  
  • Family member with stomach cancer - People with several close relatives who have had stomach cancer have a higher risk of this disease.
  • Hereditary diffuse gastric cancer - Hereditary diffuse gastric cancer is an inherited stomach cancer that tends to affect most of the stomach rather than one part. People with this condition have a 70 percent to 80 percent risk of developing gastric cancer.
  • Hereditary non-polyposis colorectal cancer (Lynch syndrome) - People with this condition have a much higher risk of colorectal and a higher risk of certain other cancers, including gastric cancer.
  • Familial adenomatous polyposis - People with this inherited condition tend to develop more than 100 adenomatous colon polyps, or masses inside the intestinal tract and sometimes in the stomach and/or small intestines. People with this condition have almost a 100 percent chance of developing colorectal cancer if they are not treated for the condition. They also have an increased risk of gastric cancer.
    
• Gender - Men are almost twice as likely to develop gastric cancer as women.
• Geography - Stomach cancer is more common in Japan, Southern and Eastern Europe, and South and Central America than in Western Europe, North America, and South-Central Asia.
• H. Pylori infection - Infection with H. pylori, a type of bacteria, is a major cause of stomach cancer.
• Obesity - Men who are very overweight or obese seem to have a higher risk of gastric cancer. Scientists are not sure whether obesity also increases a woman’s risk of gastric cancer.
• Occupational exposure - Workers in the coal, metal, and rubber industries have a higher risk of gastric cancer.
• Previous surgery or health conditions:
  • Achlorhydria - People with this condition lack hydrochloric acid, which helps digest food, in their gastric juices.
  • Chronic atrophic gastritis - Long-term infection with H. pylori cancer can lead to atrophic gastritis, a condition in which the stomach lining is damaged, less stomach acid is produced, and some or all of the stomach glands are destroyed.
  • Epstein-Barr virus infection - This virus causes mononucleosis, commonly known as mono. About 5 percent to 10 percent of people with gastric cancer have an Epstein-Barr virus infection.
  • Ménétrier’s disease (hypertrophic gastropathy) - In Ménétrier’s disease, low levels of stomach acid cause large folds in the stomach lining.
  • Pernicious anemia - People who have pernicious anemia do not make enough red blood cells because they do not have enough vitamin B₁₂.
  • Stomach surgery - People who have had part of their stomach removed to treat a noncancerous disease, such as an ulcer, are more likely to develop stomach cancer.
    
• Stomach polyps - Adenomatous polyps, or adenomas, are noncancerous growths on the stomach lining. They can sometimes become cancerous.
• Tobacco and alcohol - People who smoke have twice the gastric cancer risk of nonsmokers. Drinking excessive amounts of alcohol can also increase gastric cancer risk.
  

This content has been reviewed and approved by Myo Thant, MD.