Can Crohn's disease cause cancer?

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People with IBD have an increased risk of cancer. The exact percentages are difficult to establish, but people have more chance of developing cancer if IBD affects more of their colon.

According to the Crohn’s and Colitis Foundation, a recent study demonstrated a 7% risk of colorectal (bowel) cancer in people with IBD after 30 years of the disease. The organization also notes that people who have had Crohn’s disease for 8 years have an increased risk of cancer if more than one-third of their colon is involved.

Crohn’s & Colitis UK notes that another recent study estimated how many people with IBD that affects all or much of the large bowel go on to develop cancer. The researchers found that this depended on the duration of IBD:

• After 10 years of living with IBD: 1 person in 100
• After 20 years: 2 people in 100
• After more than 20 years: 5 people in 100

Learn the early signs of colorectal cancer here.

A 2020 review in Digestion suggested that because colorectal cancer is the third most common type of cancer worldwide, it might occur in people with IBD by chance. However, there is a clear link between colorectal cancer and inflammation in IBD.

Inflammation in the colon can cause continuous turnover of the intestinal lining cells, which increases the chance of irregularities that cause cancer, explains the Crohn’s and Colitis Foundation. Furthermore, the 2020 review above indicates that the immunosuppressive drugs that doctors prescribe for Crohn’s disease show carcinogenic properties. Due to this, they can cause uncontrolled growth of white blood cells, altered DNA, and cancers such as skin cancer and lymphoma.

Infectious agents

Some research indicates that a pathogen in livestock called Mycobacterium avium subspecies paratuberculosis (MAP) can cause Crohn’s disease and colorectal cancer. The author of a 2018 review note that doctors have identified MAP organisms in people with IBD and cancer and that these organisms cause changes in the lining of the digestive tract.

Another review suggests that the waterborne and foodborne zoonotic transmission of MAP from livestock to humans is a risk to public health. The author concludes that although no conclusive evidence exists, MAP may be a plausible infectious agent associated with IBD and other autoimmune disorders.

Researchers are continuing to investigate the interplay between infectious agents, the gut microbiome, and gut inflammation to build their understanding of the link between Crohn’s disease and cancer.

Crohn’s & Colitis UK outlines the risk factors for bowel cancer in people with IBD:

• The severity of inflammation: There is an increased risk of bowel cancer in people with more severe inflammation.
• A family history of the disease: The risk is most significant for people with a parent or sibling who had bowel cancer under the age of 50 years.
• Primary sclerosing cholangitis (PSC): PSC is an inflammatory condition that involves the bile ducts and affects 1 in 50 people with Crohn’s disease. People with PSC have an increased risk of cancer.
• Sex: Males have a slightly greater risk of developing bowel cancer than females.
• Age: People over the age of 50 years have a higher risk of developing bowel cancer.

Learn more about the risk factors of bowel cancer here.

Effect on outlook

A large Scandinavian population-based study that features in The Lancet found that people with both Crohn’s disease and colorectal cancer have a higher mortality rate than those without Crohn’s disease who receive a colorectal cancer diagnosis.

The authors suggest that doctors should focus cancer screening on people who:

• receive a Crohn’s disease diagnosis before the age of 40 years
• have colon inflammation
• have PSC

It is important to remember that these are the findings of one study. An individual’s outlook will depend on many factors, including the progression and severity of the condition. Anyone who feels concerned about their outlook can discuss this with their doctor.

Learn more about the likelihood of potentially fatal complications in Crohn’s disease.

Experts recommend that people with Crohn’s disease have regular screenings for cancer because early detection is key to a better outcome. People with this condition can reduce their risk of developing cancer by:

• seeing a gastroenterologist at least once a year
• having regular colonoscopies
• keeping a list of symptoms or concerns to discuss with a doctor
• continuing to take medications that a doctor has prescribed
• exercising regularly
• eating a well-balanced, high fiber diet
• reducing the intake of red and processed meat
• limiting alcohol consumption
• stopping smoking, if applicable
• taking a vitamin D supplement if a doctor has diagnosed low levels
• notifying a doctor if a family member develops colorectal cancer

Learn about diagnostic tools for bowel cancer here.

As people with Crohn’s disease have an increased risk of bowel cancer, they should ensure that they have regular screenings and visit their gastroenterologist at least once a year.

Although some research links immunosuppressant medications to an increased risk of cancer, it is important to continue to take any prescribed medication unless a doctor says otherwise. Medication helps keep inflammation and other symptoms under control.

A person can reduce the risk of bowel cancer by eating a balanced, fiber-rich diet, avoiding smoking and excessive alcohol, and keeping physically active.