A chronic digestive condition affecting approximately one in 400 Americans, Crohn's disease, has been associated with a heightened risk of developing various cancers. The incurable inflammatory bowel disease (IBD) causes inflammation in the digestive tract and affects about one million people in the U.S.
A large Swedish study tracking nearly 40,000 patients over seven years has found that individuals with Crohn's disease face a higher cancer rate compared to the general population, irrespective of whether they have been treated with immune-suppressing drugs. The findings, published in the American Journal of Gastroenterology, analyzed national health databases to compare cancer rates in Crohn's patients with a matched control group of over 360,000 individuals without IBD.
The study indicated an elevated risk for blood cancers, as well as cancers of the lung, small bowel, liver, and bile ducts. A particularly strong link was observed with skin cancers, specifically squamous and basal cell carcinomas. After excluding non-melanoma skin cancers, the study reported roughly one extra cancer diagnosis per 1,000 Crohn's patients annually. This excess risk appears to be primarily driven by the persistent inflammation characteristic of the disease itself, rather than by the medications used for treatment.
Chronic inflammation can damage cellular DNA over time, promote abnormal cell growth, and create an environment conducive to tumor development. While the increased risk is noted as modest, the number of Americans living with Crohn's disease is substantial and growing. A 2024 study tracking Crohn's disease rates in the Medicaid population found that prevalence more than tripled between 2010 and 2019 among nearly 200,000 beneficiaries.
Researchers divided Crohn's patients into groups based on treatment history, including those who had never taken immunosuppressive drugs and those who had used medications such as thiopurines, Humira, vedolizumab, or ustekinumab. The study found that even patients who had never taken these drugs exhibited higher cancer rates than healthy individuals, further suggesting the disease itself is a major factor.
Blood cancer risk was particularly elevated, with patients who used immunosuppressants like Humira facing nearly three times the risk of lymphoma compared to healthy individuals. Those on thiopurines had about 1.5 times the risk. Hepatobiliary cancers, including those of the liver and bile ducts, also showed a higher risk across the board for Crohn's patients, regardless of treatment.
The study noted no significant increase in cancer risk among pediatric patients under 18, which may offer reassurance to younger individuals and their families. However, for adults, the risk increased with age, highlighting the importance of regular screenings.
The researchers acknowledged several limitations, including a follow-up period of just over seven years, which might be insufficient to capture cancers with longer development times. They also noted that patients were categorized as 'treated' for the entire study duration once they began a medication, even if they later stopped, which could underestimate the true risk of certain drugs. As an observational study, it could not fully rule out other contributing factors like smoking and obesity. Additionally, because the study was conducted in Sweden, which has a lower cancer rate than the U.S., the findings may not directly translate to American patients.