Does IBD raise my risk of bowel cancer, and how often should I have a colonoscopy?
Long-standing inflammation in the colon does raise the risk of bowel cancer, but it helps to keep this in proportion: most people with IBD never develop it. The risk is higher when colitis affects most of the colon and has been present for many years, and it is lower for people whose disease does not involve the colon. The reassuring part is that this risk is managed. People at higher risk are offered a regular surveillance colonoscopy, usually every one to three years depending on individual risk factors, which can catch early changes long before they would become a problem.
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This is an understandable fear, and the honest answer holds two truths at once: there is a raised risk, and most people with IBD never get bowel cancer. Both are true, and the second is easy to lose sight of.
Who has a higher risk
The extra risk comes from long-standing inflammation in the colon. Crohn's & Colitis UK explains that risk is "highest when inflammation affects all, or most, of your colon," and that it "starts to increase about eight years after the start of your symptoms" (Crohn's & Colitis UK). People whose disease does not involve the colon do not carry this raised risk.
Keeping the numbers in proportion
The figures are more reassuring than the fear suggests. Crohn's & Colitis UK gives roughly "1 in every 100" people with colitis developing bowel cancer after 10 years of symptoms, "2 in every 100" after 20 years, and "5 in every 100" after more than 20 years (Crohn's & Colitis UK). The 2025 British Society of Gastroenterology guideline adds that the risk is "much lower than previously" thought, and that "not all patients have increased risk" (BSG).
How it is watched: surveillance colonoscopy
This is the key point. The risk is actively managed rather than left to chance. People at higher risk are offered a surveillance colonoscopy "every 1 to 3 years" depending on individual risk factors (Crohn's & Colitis UK). These checks look for early changes that can be dealt with long before they would become cancer.
- Ask your team whether and how often you need surveillance, since it depends on how much of your colon is involved and for how long.
- Keeping inflammation controlled is itself part of lowering the risk.