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Small Intestine Cancer Causes, Risk Factors, and Prevention
Learn about the risk factors for small intestine cancer and what you might be able to do to help lower your risk.
This information is about small intestine cancers called adenocarcinomas. To learn about other types of cancer that can start in the small intestine, see Gastrointestinal Carcinoid Tumors, Gastrointestinal Stromal Tumors, or Non-Hodgkin Lymphoma.
What causes small intestine cancer (adenocarcinoma)?
While there are several known risk factors for small intestine adenocarcinoma, not much is known about exactly what causes these cancers. In fact, many experts wonder why it’s so rare. The small intestine is the longest part of the gastrointestinal (GI) tract, yet only a very small percentage of GI adenocarcinomas start here.
Gene changes that may lead to small intestine cancer
Cancer is caused by changes in genes – the pieces of DNA inside each cell that carry instructions for how the cell works. Certain genes control when our cells grow, divide to make new cells, or repair mistakes in DNA. They also cause cells to die when they’re supposed to. If these genes aren’t working properly, it can lead to cells growing out of control.
Cancer develops when changes (mutations) in certain genes lead to abnormal cell growth. For more about how genes changes can lead to cancer, see Genes and Cancer.
Changes in many different genes are usually needed to cause small intestine cancer.
Inherited (germline) vs. acquired (somatic) gene changes
Gene changes can either be inherited from a parent or acquired during a person’s life.
A very small portion of small intestine cancers are caused by inherited gene mutations. See risk factors below for more on these.
However, most small intestine cancers are caused by gene changes acquired during a person’s life, not inherited. These changes only affect cells that come from the original mutated cell and are not passed down to a person’s children. Certain risk factors probably play a role in causing these acquired gene changes, but so far it’s not known what causes most of them.
Risk factors for small intestine cancer
A risk factor is anything that raises your chances of getting a disease such as cancer. Some risk factors, such as your age or inherited genetic syndromes, cannot be changed. But in some cases, there may be ways to lower your risk.
Keep in mind that having a risk factor, or even several, does not mean that a person will get the disease. And some people who get the disease may not have any known risk factors.
Because small intestine adenocarcinoma is so uncommon, risk factors for this disease have been hard to study. Some of the known risk factors include:
Smoking and alcohol use
Some studies have found an increased risk with either smoking or drinking alcohol, but not all studies have found this. If you smoke and want to know more about quitting, see How to Quit Using Tobacco.
Diet
Some research has suggested that diets high in red meat and salted or smoked foods might raise the risk of small intestine cancer. Following a healthy eating pattern that includes plenty of fruits, vegetables, and whole grains probably lowers risk.
Celiac disease
For people with celiac disease, eating gluten (a protein found in wheat and some other grains) causes the body's immune system to attack the lining of the intestines. People with celiac disease have an increased risk of a certain kind of lymphoma of the intestine called enteropathy-associated T-cell lymphoma. They may also have an increased risk of small intestine adenocarcinoma.
Colon cancer
People who have had colon cancer have an increased risk of getting cancer of the small intestine. This could be due to shared risk factors.
Crohn's disease
Crohn's disease is a condition in which the immune system attacks the gastrointestinal (GI) tract. This disease can affect any part of the GI tract, but it most often affects the lower part of the small intestine. People with this condition have a much higher risk of small intestine cancer, particularly adenocarcinoma. These cancers are most often seen in the ileum, the last part of the small intestine near the colon.
Inherited syndromes
People with certain inherited conditions have a higher risk of small intestine cancer (mainly adenocarcinoma).
In FAP, many (often hundreds) of polyps develop in the colon and rectum. If the colon isn’t removed, 1 or more of these polyps will become cancerous. Polyps can also develop in the stomach and small intestine, and can lead to cancers in these areas. In people with FAP, most small intestine cancers are found in the duodenum. This condition is caused by an abnormal change in the APC gene.
In most cases, Lynch syndrome is caused by a defect in 1 of several mismatch repair (MMR) genes, such as MLH1, MSH2, MSH6, PMS1, or PMS2. Having an abnormal version of any these genes reduces the body’s ability to repair damage to its DNA. This results in an increased risk of cancer of the colon and small intestine, as well as a high risk of endometrial and ovarian cancer.
People with PJS develop polyps in the stomach and intestines, as well as in other areas including the nose, the airways of the lungs, and the bladder. They can also have dark freckle-like spots on the lips, inner cheeks, and other areas. PJS can increase the risk of many types of cancer, including small intestine adenocarcinoma. This syndrome is caused by changes in the STK11 (LKB1) gene.
People with MUTYH-associated polyposis develop colon polyps that will almost always become cancerous if the colon is not removed. They also can get polyps in the small intestine and have an increased risk of small intestine cancer. People with this syndrome can also get cancers of the skin, ovary, and bladder. This syndrome is caused by mutations in the MUTYH gene.
People with this condition have severe lung problems. Often, their pancreas cannot make the enzymes that break food down so that it can be absorbed. People with CF have an increased risk of small intestine cancer. A child must have 2 abnormal copies of the CFTR gene (1 from each parent) to get this disease.
Since many of these syndromes are linked to small intestine cancer at a young age as well as other types of cancer, finding out whether these syndromes run in a family can help people take action early. Knowing about a family syndrome can guide decisions about screening and other steps to lower cancer risk.
Genetic tests can find gene changes linked to these conditions. Before testing, it’s best to talk with a qualified cancer genetics professional who can explain what the results might mean for you and your family. To learn more, see Genetic Testing for Cancer Risk.
Can small intestine cancer (adenocarcinoma) be prevented?
There are currently no known ways to prevent most small intestine adenocarcinomas. However, there are some lifestyle-related factors that might increase the risk for these cancers. Making healthier choices such as avoiding tobacco and alcohol, and limiting red meat might lower your risk. Small intestine cancers are rare to begin with, but these healthy choices might also lower your risk of some other types of cancer.
Excess body weight (overweight or obesity) may increase the risk of small intestine cancer. Staying at a healthy weight may help lower your risk.
Overall, diets that are high in vegetables, fruits, and whole grains, and low in red and processed meats, likely lower small intestine cancer risk, although it’s not exactly clear which factors are important. Many studies have found a link between red meats (beef, pork, and lamb) or processed meats (such as hot dogs, sausage, and lunch meats) and increased cancer risk.
Limiting red and processed meats and eating more vegetables, fruits, and whole grains may help lower your risk.
See the American Cancer Society Guidelines for Diet and Physical Activity for Cancer Prevention to learn more.
Several studies have found a higher risk of small intestine cancer with increased alcohol intake. It is best not to drink alcohol. For people who do drink, they should have no more than 1 drink per day for women or 2 drinks per day for men. Not drinking alcohol may help reduce your risk.
Quitting smoking may help lower your risk of small intestine cancer and many other types of cancer, too. If you smoke and would like help quitting, call the American Cancer Society at 1-800-227-2345.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
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Last Revised: February 9, 2026
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