Childhood-onset inflammatory bowel disease (IBD) is known to cause painful gastrointestinal symptoms, but a new study of Swedish patients finds that it also is associated with an increased risk of cancer.
According to the study, published in the BMJ, the rates of colorectal cancer (CRC) among adults with IBD are declining, perhaps due to guidelines recommending frequent surveillance colonoscopies. However, little research has explored whether childhood-onset IBD is associated with a higher risk of cancer—colorectal or any other type.
The researchers set out to fill this gap in the literature by conducting a nationwide cohort study based on Swedish Patient Register data from 1964 to 2014. They collected information on diagnosis of IBD in childhood, relevant surgeries and drugs, family history of cancer, and eventual diagnosis of cancer.
Across the 5 decades of data, 9405 patients with childhood-onset IBD were identified: 49% had ulcerative colitis, 41% had Crohn’s disease, and the rest had unclassified IBD. These patients were matched to up to 10 reference individuals by sex, year of birth, and place of residence. The rate of primary cancers in the IBD group was 3.3 per 1000 person-years, compared with 1.5 per 1000 person-years in the matched group. In other words, there was an additional case of cancer for every 556 patients with IBD followed for a year compared with the reference patients.
Patients with childhood-onset IBD had a 2.2-fold higher relative risk of cancer, and the risk was higher among those with ulcerative colitis rather than Crohn’s disease. The hazard ratio for cancer was higher for those who were younger in age when they were first diagnosed with IBD. The researchers also found that several disease phenotypes were associated with higher cancer risk, such as primary sclerosing cholangitis.
There was an increased risk of specific cancers associated with IBD, particularly CRC, small intestinal cancer, and liver cancer. Overall, there was a hazard ratio of 18.0 for gastrointestinal cancers in those with childhood-onset IBD.
The study authors hypothesized that some types of cancers may be detected earlier due to the endoscopies recommended for patients with IBD, which could partly explain the higher cancer rates. They also noted that the severity and duration of chronic inflammation may drive cancer risk. The authors recommend that their findings be taken into account when creating strategies for cancer surveillance.
According to an accompanying editorial, this “thoughtful and thorough investigation” should be used to inform the design of other cohort studies of patients with childhood-onset IBD to strengthen the evidence supporting increased cancer risk.
“International efforts to confirm the findings of this Swedish cohort and extend their reach to the increasing number of children diagnosed as having inflammatory bowel disease globally will help to improve decision making for the many patients and their families who must choose between different options for both treatment and surveillance,” the editorial concluded.