A risk factor is something (such as a behaviour, substance or condition) that increases the risk of developing cancer. Most cancers are the result of many risk factors, but sometimes small intestine cancer develops in people who don’t have any of the risk factors described below.
The risk of developing small intestine cancer increases with age. The average age of diagnosis is about 60. Men develop small intestine cancer slightly more often than women.
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.
There is convincing evidence that the following factors increase your risk for small intestine cancer.
Familial adenomatous polyposis (also known as familial polyposis or FAP) is an inherited condition caused by a mutation of the adenomatous polyposis coli (APC) genegeneThe basic biological unit of heredity passed from parents to a child. Genes are pieces of DNA and determine a particular characteristic of an individual.. FAP causes hundreds to thousands of polyps to develop on the lining of the colon (part of the large intestine) and rectum. These polyps have the potential to develop into cancer. Each polyp is no more likely to develop into cancer than polyps in people who don’t have FAP. However, the large number of polyps means there is a greater risk that cancer could develop.
FAP can also cause polyps to grow in the small intestine. People with FAP are at higher risk of developing adenocarcinoma of the small intestine. Most small intestine tumours linked to FAP develop in the duodenum (the first part of the small intestine).
Lynch syndrome (also called hereditary non-polyposis colorectal cancer, or HNPCC) is an inherited condition caused by mutations in some of the genes that repair damage to DNA. Lynch syndrome causes polyps to grow in the lining of the colon (part of the large intestine) and rectum, but not as many polyps as in FAP.
Lynch syndrome puts people at high risk for developing colon and other cancers, including small intestine cancer. People with Lynch syndrome have up to a 4% greater risk of developing small intestine cancer compared to people in the general population. Small intestine cancer often occurs at a younger age in people with Lynch syndrome.
Crohn’s disease is an inflammation of the gastrointestinal tract. It commonly affects the small intestine, especially the ileum (the last part of the small intestine). People with Crohn’s disease have an increased risk of developing small intestine cancer.
Generally, small intestine cancer occurs at a younger age in people with Crohn’s disease. However, the risk of small intestine cancer does not generally increase until a person has had Crohn’s disease for more than 10 years.
Celiac disease (sprue) damages the small intestine so that it doesn’t absorb nutrients from food as well as it should. People with celiac disease are sensitive to gluten (a protein found in grains such as wheat, rye and barley). They also have an increased risk of enteropathy associated T cell lymphoma (EATL) and adenocarcinoma tumours in the small intestine. These tumours most often develop in the jejunum (the middle part of the small intestine).
Peutz-Jeghers syndrome is a rare inherited condition. People with Peutz-Jeghers syndrome have a mutation of the STK11 (also called LKB1) gene. The STK11 gene is normally involved in making a tumour suppressor enzyme. This enzyme helps control cell growth and keeps cells from growing and dividing too fast. Mutations in the STK11 gene prevent this enzyme from working properly so that cells divide too often. People with Peutz-Jeghers syndrome often have hamartomas (a special kind of polyp) form in their intestine. These polyps increase the risk of developing colorectal and small intestine cancer.
People with Peutz-Jeghers syndrome have about an 18 times greater risk of developing small intestine cancer compared to people in the general population.
Neurofibromatosis type 1 (also called von Recklinghausen disease) is an uncommon inherited condition that affects the nerves, muscles, bones and skin. It is caused by a mutation in the NF1 gene, which is a tumour suppressor gene. People with neurofibromatosis type 1 have a higher risk of developing certain cancers. The condition has been linked to small intestine cancer, particularly gastrointestinal stromal tumours (GIST).
People with a weakened immune system have a higher risk of developing some types of cancer, including small intestine cancer. The immune system can become weakened for a number of reasons, including AIDS (acquired immunodeficiency syndrome). People with AIDS have a greater risk of developing lymphoma of the small intestine.
Cystic fibrosis is a genetic condition that affects glands that make mucus and sweat, which can in turn affect how well the lungs and digestive tract function. People with cystic fibrosis have a higher risk of developing small intestine cancer. There is also some evidence that suggests people with cystic fibrosis have a greater risk for small intestine cancer after they receive an organ transplant. However, the overall risk of small intestine cancer in people with cystic fibrosis is still very low.
People who have a personal history of other cancers, particularly colorectal cancer, have a higher risk of small intestine cancer. However, the overall risk of small intestine cancer is still low.
The following factors have been linked with small intestine cancer, but there is not enough evidence to say they are known risk factors. Further study is needed to clarify the role of these factors for small intestine cancer.
Some studies have reported that people who eat a diet high in fat – especially animal fat – may have a higher risk of small intestine cancer. Researchers have also found that people who eat large amounts of red meat develop small intestine cancer more often than people who eat less red meat.
There is conflicting evidence on the link between small intestine cancer and being overweight or obese. Some studies suggest that having a higher body mass index (BMI) may increase the risk of developing small intestine cancer.
It isn’t known whether or not the following factors are linked with small intestine 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 small intestine cancer:
To make the decisions that are right for you, ask your healthcare team questions about risks.
The Canadian Cancer Society is actively lobbying the federal government to establish a national caregivers strategy to ensure there is more financial support for this important group of people.