Monitoring & follow-up
Living with Crohn's disease means managing inflammation, but it also means understanding how chronic inflammation affects long-term cancer risk. The relationship between Crohn's and cancer is more nuanced than many patients realize. Colorectal cancer gets the most attention, and rightly so, but Crohn's patients also face a rare but elevated risk of small bowel cancer and a small medication-related lymphoma risk that deserves honest discussion. Knowing what to watch for and when to start surveillance puts you in a stronger position to catch problems early.
Colorectal Cancer Risk Depends on Where Crohn's Affects Your Colon
The colorectal cancer risk for Crohn's patients is driven primarily by two factors: how much of the colon is involved and how long you've had the disease. A meta-analysis published in Alimentary Pharmacology & Therapeutics found that patients with Crohn's disease affecting the colon had a relative risk of 4.5 for colorectal cancer, while patients with disease limited to the ileum had a relative risk close to 1.1, meaning essentially no elevated risk.
This distinction matters. If your Crohn's involves at least one-third of your colon, your colorectal cancer risk profile looks similar to someone with ulcerative colitis. If your disease is confined to the small bowel, your colon cancer risk is close to the general population's.
Other factors that raise your individual risk include a family history of colorectal cancer, a concurrent diagnosis of primary sclerosing cholangitis (PSC), and being diagnosed with Crohn's before age 40. Ongoing active inflammation is also a significant driver. The good news: better disease control through modern therapies may be reducing colorectal cancer rates in IBD patients compared to earlier decades, according to a 2013 meta-analysis of population-based cohort studies.
When Surveillance Colonoscopy Should Start
The 2025 ACG Clinical Guideline for Crohn's Disease recommends that patients with Crohn's colitis begin surveillance colonoscopy 8 years after disease onset, provided that more than 30% of the colon is involved. After that initial screening, colonoscopies are typically repeated every 1 to 3 years depending on your risk factors.
Modern surveillance has moved away from random biopsies across the colon. Current guidelines favor high-definition colonoscopy with targeted biopsies of visible abnormalities, and in some cases chromoendoscopy, where dye is sprayed onto the colon lining to highlight subtle changes. Research published in Inflammatory Bowel Diseases has shown that roughly 90% of dysplasia in IBD patients is now detected through targeted biopsies of visible lesions rather than random sampling.
Your gastroenterologist should be tailoring the surveillance interval to your specific situation. Patients with PSC, a history of prior dysplasia, or extensive colonic involvement may need annual colonoscopies, while lower-risk patients might go 2 to 3 years between exams.
Small Bowel Cancer: Rare but Worth Understanding
Small bowel adenocarcinoma is uncommon in the general population, and it remains rare even among Crohn's patients. But the relative risk is striking. A meta-analysis in Alimentary Pharmacology & Therapeutics found that Crohn's patients have a relative risk of 33.2 for small bowel cancer compared to the general population. That high relative number reflects a very low baseline: the absolute risk is still quite small.
The typical profile involves patients who have had ileal Crohn's for 12 to 24 years, though research published in the World Journal of Gastroenterology notes that 14 to 17% of cases develop within the first 5 years. Male sex, chronic fistulous disease, and surgically bypassed loops of bowel are additional risk factors.
The challenge with small bowel cancer is detection. Standard colonoscopy can reach the terminal ileum but cannot visualize the rest of the small bowel. Symptoms like new or worsening obstruction, unexplained weight loss, or bleeding in a patient with longstanding small bowel Crohn's should prompt further investigation with imaging such as CT enterography or MR enterography.
Medication-Related Lymphoma Risk
Some Crohn's medications carry a small but real increase in lymphoma risk, and this topic generates significant anxiety. The evidence, drawn from a large study published in JAMA, shows that thiopurines (azathioprine and 6-mercaptopurine) used alone are associated with a modestly increased lymphoma risk, anti-TNF agents used alone carry a similar small increase, and combination therapy with both raises the risk further.
The most concerning form is hepatosplenic T-cell lymphoma (HSTCL), a rare and aggressive cancer. FDA data from 2002 to 2017 identified 62 cases among IBD patients, with the majority occurring in young men with Crohn's disease who had been on thiopurine therapy. The European Crohn's and Colitis Organisation recommends limiting combination thiopurine and anti-TNF therapy to 2 years when possible to reduce this risk.
Context is essential here. The absolute lymphoma risk remains very low, and for most patients the benefits of controlling Crohn's inflammation, which itself drives cancer risk, outweigh the medication-related risk. This is a conversation to have with your gastroenterologist, weighing your age, sex, disease severity, and treatment history.
What You Can Do
Cancer risk with Crohn's is real but manageable with the right surveillance and awareness. Stay current with your colonoscopy schedule if you have colonic involvement. Report new or changing symptoms, especially unexplained weight loss, new obstructive symptoms, or rectal bleeding that differs from your usual pattern, to your gastroenterologist promptly. If you're on combination immunosuppressive therapy, discuss the timeline for potential de-escalation at your next appointment.
Track your colonoscopy schedule and results in Aidy. Knowing your surveillance timeline and bringing complete symptom history to your prep appointments helps your GI make the best decisions.