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A risk factor
is anything that affects your chance of getting a disease such as
cancer. Different cancers have different risk factors. For example,
exposing skin to strong sunlight is a risk factor for skin cancer.
Smoking is a risk factor for a number of cancers.
But risk factors don't tell us everything. Having a risk
factor, or even several risk factors, does not mean that you will get
the disease. And many people who get the disease may not have had any
known risk factors.
Scientists have found several risk factors that make a person
more likely to get stomach cancer. Some of these can be controlled, but
others cannot.
Helicobacter pylori infection
Infection with Helicobacter
pylori (H.
pylori) bacteria seems to be a major cause of stomach
cancer, especially cancers in the lower (distal) part of the stomach.
Long-term infection of the stomach with this germ may lead to
inflammation (chronic atrophic gastritis) and pre-cancerous changes of
the inner lining of the stomach. Patients with stomach cancer have a
higher rate of infection than people without this cancer. H. pylori infection
is also linked to some types of lymphoma of the stomach. Even so, the
vast majority of people who carry this germ in their stomachs never
develop cancer.
Gender
Stomach cancer is more common in men than in women.
Aging
There is a sharp increase in stomach cancer after the age of
50. Most people diagnosed with stomach cancer are in their late 60s,
70s, and 80s.
Ethnicity
In the United States, stomach cancer is more common in
Hispanic Americans and African Americans than in non-Hispanic whites.
It is most common in Asian/Pacific Islanders.
Geography
Where you live may be important. Stomach cancer is more common
in Japan, China, Southern and Eastern Europe, and South and Central
America. This disease is less common in Northern and Western Africa,
South Central Asia, and North America.
Diet
An increased risk of stomach cancer is seen with diets
containing large amounts of smoked foods, salted fish and meat, and
pickled vegetables. Nitrates and nitrites are substances commonly found
in cured meats. They can be converted by certain bacteria, such as H. pylori, into
compounds that have been found to cause stomach cancer in animals.
On the other hand, eating fresh fruits and vegetables that
contain antioxidant vitamins (such as A and C) appears to lower the
risk of stomach cancer.
Tobacco use
Smoking increases stomach cancer risk, particularly for
cancers of the upper portion of the stomach closest to the esophagus.
The rate of stomach cancer is about doubled in smokers.
Obesity
Being very overweight or obese has emerged as a possible cause
of cancers of the cardia (the part of the stomach nearest the
esophagus), but the strength of this link is not yet clear.
Previous stomach surgery
Stomach cancers are more likely to develop in people who have
had part of their stomach removed to treat non-cancerous diseases such
as ulcers. This may be because it allows more nitrite-producing
bacteria to be present. Also, acid production goes down after ulcer
surgery, and there may be reflux (backup) of bile from the small
intestine into the stomach. The risk continues to increase for as long
as 15 to 20 years after surgery.
Pernicious anemia
Certain cells in the stomach lining normally make intrinsic
factor (IF), which is a substance needed to absorb vitamin B12 from
foods. People without enough IF may end up with a vitamin B12
deficiency, which affects the body's ability to make new red blood
cells. This condition is called pernicious anemia. Along with anemia
(low red blood cell counts), there is an increased risk of stomach
cancer for patients with this disease.
Menetrier disease (hypertrophic gastropathy)
This is a condition in which excess growth of the stomach
lining leads to the formation of large folds in the lining and to low
levels of stomach acid. Because this disease is very rare, the exact
increase in the risk of stomach cancer is not known.
Type A blood
Blood type groups refer to certain substances that are
normally present on the surface of red blood cells and some other types
of cells. These groups are important in matching blood for
transfusions. For unknown reasons, people with type A blood have a
higher risk of getting stomach cancer.
Inherited cancer syndromes
Several inherited conditions may raise a person's risk of
stomach cancer.
Hereditary
diffuse gastric cancer is an inherited condition that
greatly increases the risk of developing stomach cancer. This condition
is quite rare, but the lifetime stomach cancer risk among affected
people is about 70% to 80%. Researchers recently discovered the gene
(E-cadherin/CDH1) responsible for this condition, and genetic testing
is available at some cancer centers.
Hereditary
non-polyposis colorectal cancer (HNPCC, also known as
Lynch syndrome) and familial
adenomatous polyposis (FAP) are also inherited genetic
disorders. They cause a greatly increased risk of getting colorectal
cancer and a slightly increased risk of getting stomach cancer in
family members who have these gene mutations.
People who carry mutations of the inherited breast cancer
genes BRCA1 and BRCA2 may also have a higher rate of stomach cancer.
Family history of stomach cancer
People with several first-degree relatives who have had
stomach cancer are more likely to develop this disease.
Some types of stomach polyps
Polyps are non-cancerous growths on the lining of the stomach.
Most types of polyps (such as hyperplastic polyps or inflammatory
polyps) do not appear to increase a person's risk of stomach cancer,
but adenomatous polyps -- also called adenomas -- can sometimes develop
into cancer.
Epstein-Barr virus infection
This virus causes infectious mononucleosis ("mono"). Almost
all adults have been infected with this virus at some time in their
lives, usually as children or adolescents. It has been linked to some
forms of lymphoma. Epstein-Barr virus has also been found in the
stomach cancers of about 5% to 10% of people with this disease. These
people tend to have a slower growing, less aggressive cancer with a
lower tendency to spread. It isn't clear what role the virus plays in
the development of stomach cancer.
Certain occupations
Workers in the coal, metal, and rubber industries seem to have
a higher risk of getting stomach cancer.
Last Medical Review: 11/07/2008 Last Revised: 11/07/2008
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