Risk factors for stomach cancer
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. Helicobacter pylori infection is the most important risk factor for stomach cancer.
More men than women develop stomach cancer. The risk of developing stomach cancer increases with age. It is greatest after 50 years of age. Some studies show that low socio-economic status is linked with a higher rate of stomach cancer.
Stomach cancer is most common in Japan, China, South America and Eastern Europe. It is not as common in North America. In Canada, the number of new cases of stomach cancer diagnosed each year has been going down since the 1980s.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
*You may wonder about coffee, tea and proton pump inhibitors (drugs that lower stomach acid). There is significant evidence showing that there is no association between these factors and stomach cancer.
Known risk factors
There is convincing evidence that the following factors increase your risk for stomach cancer.
Helicobacter pylori (H. pylori) infection is the strongest and most important risk factor for developing stomach cancer. H. pylori is a common type of bacteria found in the stomach. It can cause inflammation, ulcers and changes to cells in the lining of the stomach.
While H. pylori can increase the risk, not all people infected with H. pylori will develop stomach cancer. H. pylori may act with other factors to increase the risk of developing stomach cancer. The age when you are infected may also affect your risk of developing stomach cancer.
Find out more about Helicobacter pylori (H. pylori).
Smoking tobacco increases the risk of developing stomach cancer. The more cigarettes you smoke and the longer you smoke, the higher your risk.
Some studies have shown that exposure to second-hand smoke also increases the risk of stomach cancer.
If you have a first-degree relative who has had stomach cancer, you have a higher risk of developing stomach cancer. The higher risk may be due to inherited genetic conditions. It may also be because family members have the same risk factors such as diet, smoking and H. pylori infection.
Certain inherited genetic conditions can put you at higher risk of developing stomach cancer.
Hereditary diffuse gastric cancer (HDGC) is caused by a mutation of the CDH1 gene (also called E-cadherin gene). People with HDGC have a higher risk of developing diffuse gastric cancer. With this type of cancer, the cancer cells are spread throughout the stomach and don’t form a tumour in one area. Stomach cancer linked with HDGC usually develops before the person is 40 years of age. Doctors may suspect HDGC when stomach cancer develops in several members of a family.
Familial adenomatous polyposis (FAP) is mainly caused by a mutation of the adenomatous polyposis coli (APC) gene. People with FAP develop large numbers (hundreds to thousands) of polyps called adenomas. Most polyps develop on the lining of the colon and rectum, but they can also develop in the stomach and small intestine.
Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) is caused by mutations in the genes that correct mistakes when cells divide and DNA is copied.
Peutz-Jeghers syndrome is caused by a mutation of the STK11 gene (also called PJS or LKB1 gene). It causes polyps in the intestines and stomach.
Juvenile polyposis syndrome causes polyps to grow in the gastrointestinal (GI) tract, including the stomach. These polyps usually form before age 20. Some people with this syndrome develop only a few polyps. Other people can have over 100 polyps.
Li-Fraumeni syndrome is usually caused by a mutation in the TP53 or CHEK2 gene. It is linked with a higher risk of developing several types of cancer, including stomach cancer.
BRCA gene mutations increase the risk of developing breast or ovarian cancer. BRCA gene mutations can also increase the risk of developing other cancers, including stomach cancer, but these are much less common than breast or ovarian cancer.
The following non-cancerous stomach problems increase the risk of developing stomach cancer.
Chronic atrophic gastritis is when the lining of the stomach becomes inflamed. It is usually caused by H. pylori infection. It can also develop if the immune system attacks healthy tissues of the stomach lining by mistake (called autoimmune atrophic gastritis).
Intestinal metaplasia is when cells in the stomach are replaced by cells that normally line the intestines. It may be caused by H. pylori infection, inherited conditions, diet or other factors.
Gastric epithelial dysplasia is a precancerous condition that occurs when the cells in the stomach lining change so they are abnormal. These abnormal cells may develop into adenocarcinoma over time. Adenocarcinoma is the most common type of stomach cancer.
Adenomas, or adenomatous polyps, are a type of polyp made up of abnormal gland cells in the lining of the stomach. They are precancerous, which means that they can develop into stomach cancer. There is a greater chance that an adenoma will become stomach cancer if it is larger than 2 cm. Adenomas may be caused by an inherited condition, or they may be a symptom of other stomach problems.
Ménétrier disease is a rare disease that causes cells in the lining of the stomach to grow too much and form large folds in the lining.
Pernicious anemia is a type of anemia (a lower than normal number of red blood cells) that develops when the gastrointestinal (GI) tract can’t absorb vitamin B12. The body needs B12 to make red blood cells. People with pernicious anemia may develop polyps in the stomach.
Surgery to remove part of the stomach is called partial gastrectomy. This surgery may be used to treat stomach ulcers. People who have had stomach surgery have a higher risk of developing stomach cancer. This may be because bile from the small intestine moves into the remaining stomach and causes inflammation. It is not clear if this happens because of H. pylori infection, because the stomach makes less stomach acid or because of other reasons.
Surgery to treat ulcers in the first part of the small intestine (called the duodenum) doesn’t seem to increase the risk for stomach cancer.
Infection with EBV may increase the risk of developing non-Hodgkin lymphoma of the stomach, which is a rare type of stomach cancer. It may also increase the risk of developing adenocarcinoma, the most common type of stomach cancer.
Find out more about Epstein-Barr virus (EBV).
People who were exposed to ionizing radiation from atomic bomb explosions in Japan during the Second World War have a greater risk of developing stomach cancer, especially if they were children when they were exposed to the radiation. Studies have shown that people exposed to radiation from nuclear accidents or fallout are also at higher risk of developing stomach cancer.
Some studies suggest that people treated with some forms of radiation therapy have a higher risk of developing stomach cancer. This includes people who were treated with a radioisotope for thyroid cancer and people given external beam radiation therapy for Hodgkin disease. The risk of developing stomach cancer after radiation therapy depends on many factors. Only a very small number of people develop cancer because of radiation therapy treatments. The benefit of treating a cancer often greatly outweighs the risk of developing stomach cancer later on.
People who work in the rubber manufacturing and processing industry have a higher risk of developing stomach cancer. This is because they are exposed to cancer-causing chemicals commonly used in the rubber industry.
People with type A blood have a higher risk of developing stomach cancer, although the reason for this association is not known.
Possible risk factors
The following factors have been linked with stomach cancer, but there is not enough evidence to show they are known risk factors. Further study is needed to clarify the role of these factors for stomach cancer.
There is some evidence that eating salt and salty foods, including salt-preserved and salted foods, may increase the risk for stomach cancer. There is also a link between salt intake and developing intestinal metaplasia.
Researchers are not sure if salt is an independent risk factor. This means that they don’t know if salt increases your risk for stomach cancer on its own, or if it increases the risk when it is combined with other risk factors like H. pylori.
Studies also link the lack of food refrigeration to a higher risk for stomach cancer. This is probably because people who don’t have access to refrigeration often use salt to preserve their food.
Some studies show that eating smoked, cured and processed meats may increase the risk for stomach cancer. This may be due to compounds like nitrates, heterocyclic amines and polycyclic aromatic hydrocarbons, which are often found in these meats.
Some studies have shown that drinking alcohol increases the risk of stomach cancer. The risk is increased with more than 3 drinks a day.
There is some evidence that obesity or a high body mass index (BMI) may increase the risk of developing stomach cancer, especially in the first part of the stomach near the esophagus (called the gastric cardia).
GERD is a condition in which the contents of the stomach, including stomach acid, back up into the esophagus and cause heartburn and discomfort in the upper abdomen or chest. The stomach acid can damage tissue in the esophagus.
GERD is a risk factor for cancer of the esophagus. Recent studies suggest that GERD may also increase the risk for cancer in the first part of the stomach (called the gastric cardia) and in the area where the esophagus joins the stomach (called the gastroesophageal, or GE, junction).
Research studies are starting to show that occupational lead exposure increases the risk of stomach cancer.
Asbestos is known to cause cancer in people. Long-term and frequent exposure to asbestos might cause stomach cancer.
Cystic fibrosis is a genetic condition that affects glands that make mucus and sweat. It can affect how well the lungs and gastrointestinal (GI) tract function. A large study followed people with cystic fibrosis for 20 years. The study showed that they may have a higher risk of developing cancer in the area where the esophagus joins the stomach (called the gastroesophageal, or GE, junction).
Unknown risk factors
It isn’t known whether or not the following factors are linked with stomach cancer. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if the following are risk factors for stomach cancer:
- grilled and barbecued meats
- a diet low in vegetables and fruit
- lack of regular physical activity
- working in the coal mining, tin mining, or iron and steel industries
- bariatric surgery, which is surgery to the stomach to help you lose weight
Questions to ask your healthcare team
To make the decisions that are right for you, ask your healthcare team questions about risks.
A person’s parents, brothers, sisters or children.
Also called FDR.
A small growth on a mucous membrane, such as the lining of the colon, bladder, uterus (womb), vocal cords or nasal passage.
Most types of polyps are non-cancerous, but some have the potential to become cancer.
The molecules inside the cell that program genetic information. DNA determines the structure, function and behaviour of a cell.
BRCA1 and BRCA2 genes are tumour suppressor genes. Changes to genes are called mutations. Mutations of the BRCA genes are inherited from one or both parents, and these mutations increase the risk of cancer.
Women with BRCA mutations have a higher risk of breast and ovarian cancers. Men with BRCA mutations also have a higher risk of breast cancer, and may have a higher risk of prostate cancer. The risk of other cancers – such as stomach or pancreatic cancer – may also be higher with BRCA mutations.
A type of high-frequency radiation that can remove particles from matter it passes through, resulting in charged ions. These charged ions can cause changes to cells’ DNA that can damage or kill the cells.
Ionizing radiation is present in the atmosphere. It can also come from medical tests or treatments, such as x-rays or radiation therapy.
A substance or element that gives off radiation.
Radioisotopes can be used in imaging tests and cancer treatments. When a radioisotope is mixed with a medicine or drug, it is called a radiopharmaceutical.
Also called radioactive isotope.
A type of radiation therapy that uses a machine outside the body to direct radiation at a tumour and surrounding tissue.
Also called external radiation therapy or teletherapy.
A measure that relates body weight to height (calculated by dividing weight in kilograms by height in metres squared).
BMI is used to find out if people are underweight, overweight, obese or in the normal weight range for their height.
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