A chronic digestive condition that affects about one in 400 Americans has been linked to an increased risk of a range of deadly cancers.
Crohn’s disease, which causes debilitating abdominal pain, chronic diarrhea and exhaustion, is an incurable form of inflammatory bowel disease (IBD) that causes inflammation in the digestive tract and affects approximately one million Americans.
The chronic digestive disease has now been linked to an increased risk of several forms of cancer, according to a large Swedish study of almost 40,000 patients over seven years.
The findings confirm that people with Crohn’s disease have a higher rate of disease cancer than the general population, regardless of whether they have treated their condition with immunosuppressive medications.
That includes an increased risk of blood cancer, as well as cancers of the lungs, small intestine, and liver and bile ducts. The study also found a particularly strong link with skin cancer, especially squamous cell and basal cell carcinomas.
The increased risk is real but modest, with roughly one additional cancer per 1,000 patients per year, after excluding non-melanoma skin cancer.
That excess risk appears to be largely caused by the disease itself; specifically, the chronic inflammation it causesrather than by the medications used to treat it.
Over time, that persistent inflammation can damage cell DNA, promote abnormal cell growth, and create an environment in which tumors are more likely to develop.
An estimated 1 million people in the US live with Crohn’s disease, an incurable inflammatory bowel disease (stock image)
To get a clearer picture of cancer risk, the study, published in the American Journal of Gastroenterologyfollowed almost 39,000 Swedish Crohn’s patients diagnosed between 2007 and 2022 using national health databases that record every diagnosis, prescription and outcome.
They then matched each Crohn’s patient with up to ten healthy people of the same age, gender and geographic location, creating a comparison group of more than 360,000 people without any form of IBD.
Matching ensures that any differences in cancer rates can be attributed more confidently to Crohn’s disease itself, rather than to age, gender or where people live.
The researchers divided the Crohn’s patients into groups based on their treatment history, including a group consisting of people who had never taken immunosuppressants – the standard treatment for Crohn’s disease.
The other group consisted of people who had taken immunosuppressants such as thiopurines, Humira, vedolizumab or ustekinumab – or combinations thereof.
They compared cancer rates between the two groups, calculating how many additional cases occurred and how much higher the risk was for the Crohn’s patients.
They then broke down the data by cancer type, by age group, including children under 18, and by treatment history to see where the risks were greatest and where they weren’t.
Over more than seven years of follow-up, the researchers confirmed that Crohn’s patients have a higher – albeit only slightly – risk of cancer than the general population.
According to Medicaid data, women consistently had higher rates of Crohn’s disease than men throughout the 2010s
The excess risk was most pronounced for skin cancer; particularly basal and squamous cell carcinomas, which affect 3.6 million and 1.8 million Americans annually, respectively, and have a mortality rate of 0.12 percent and 4.3 percent if detected early.
Patients with Crohn’s disease had a higher rate of these cancers compared to the general population.
For basal cell carcinoma, the rate increased by 1.05 to 1.58 additional cases per 1,000 person-years, while squamous cell carcinoma increased by 0.34 to 1.17 additional cases per 1,000 person-years.
But when researchers removed these skin cancers from the equation, the picture changed.
After excluding non-melanoma skin cancers, Crohn’s patients received approximately one additional cancer diagnosis per 1,000 people annually.
The excess was largely caused by lung cancer, cancer of the small intestine, cancer of the liver, gallbladder and bile ducts, and blood cancers such as lymphoma. The study found no increased risk of colorectal, breast or prostate cancer.
Even patients who never took these drugs had higher cancer rates than healthy individuals. That suggests that the disease itself, and not the treatments, is an important driver.
Crohn’s disease is most common in middle-aged adults, with prevalence peaking between the ages of 40 and 60
For years, experts have understood that Crohn’s cancer risk involves both the disease and the medications used to treat the disease, but it has always been difficult to separate the two.
The likely reason is chronic inflammation, which over time can damage cells and increase the risk of cancer.
The risk of blood cancer was particularly high in patients with Crohn’s disease. Those who had taken immunosuppressants such as Humira had almost three times the risk of lymphoma compared to healthy people, while those who took thiopurines had about 1.5 times the risk.
For hepatobiliary cancers, including those of the liver and bile ducts, the risk was also higher in Crohn’s patients across the board, regardless of treatment.
Patients receiving vedolizumab and ustekinumab had the largest relative increase in liver cancer risk, but because the actual number of cases was small, the real additional risk remained very low for most patients.
The good news is that the study found no significant increase in cancer in pediatric patients under the age of 18, which can reassure younger patients and their families.
For adults, the risk increased with age, underscoring the importance of regular colonoscopies and whole-body skin checks, especially in older patients.
Although Crohn’s disease increases the risk of cancer compared to the general population, the absolute risk remains low, meaning that the vast majority of people with Crohn’s disease will never develop these cancers.
The researchers noted several important limitations. The study’s follow-up time of just over seven years could be too short to detect cancers that take decades to develop, meaning the longer-term risks may be underestimated.
The researchers counted patients as “treated” for the entire study once they started a drug — even if they stopped later — a conservative approach that could underestimate the true risk of each drug.
By considering patients treated even after they stop taking the drug, the study mixes unexposed time into the treated group, which can hide or weaken a true cancer link and make the medication seem less risky than it really is.
As an observational study, it followed real-world data rather than a controlled experiment, so it couldn’t completely rule out other factors such as smoking and obesity.
Because the study took place in Sweden, where cancer rates are lower than in the US, the findings may not translate directly to US patients.
Although the cancer risk associated with Crohn’s disease is modest, the number of Americans living with the disease is significant and growing.
A 2024 study tracked Crohn’s disease rates in the Medicaid population – which includes about one in four Americans – from 2010 to 2019.
Among the nearly 200,000 beneficiaries with the condition, the prevalence more than tripled from 56 to 165 per 100,000, while the rate of new diagnoses fell from 18 to 13 per 100,000 person-years.
This difference is significant. It means more Americans are living longer with a chronic condition that requires ongoing care, even as the number of new cases declines, a pattern consistent with other Western countries.
