In addition, the investigators found that chronic liver disease, longstanding colitis, and a family history of any cancer in relatives younger than 50 years of age were also strong risk factors for any cancer in patients with childhood-onset IBD. Patients had a higher risk for cancer in the first year of follow-up, likely because of improved detection and surveillance.
Type of Cancer
The investigators calculated that gastrointestinal cancer represented 40% of cancers documented in individuals with childhood-onset IBD. The hazard ratio for gastrointestinal cancers was 18.0 (95% confidence interval [CI], 14.4 - 22.7) on the basis of 202 cancers in their cohort of patients with IBD.
When the researchers examined the risk for lymphoid neoplasms in childhood-onset IBD, they found a 2.7-fold increased risk for lymphoid neoplasms (95% CI, 1.7 - 4.2) in patients with childhood-onset IBD. The relative risks for lymphoma were similar in patients diagnosed with ulcerative colitis and Crohn's disease.
Effect of Treatment
When the investigators stratified the risk for any cancer by medical treatment, they found no clear differences between groups. "We cannot rule out that thiopurines or TNF [tumor necrosis factor] inhibitors increase the risk of cancer, as our study was not big enough to recognise whether drugs are a major risk factor for cancer development in children and young adults," the authors write. "Instead, we suggest that extent and duration of chronic inflammation might be the main driving mechanisms underlying the increased risk of cancer."
In an accompanying editorial, Susan Hutfless, PhD, assistant professor of medicine at Johns Hopkins University in Baltimore, Maryland, agrees that the data are not sufficient to make a conclusion about treatments and cancer risk. "We are unable to determine the relation between cancer risk and use of immunomodulators, biological agents, or their combination owing to incomplete information on exposure to infliximab, as well as insufficient follow-up and power," she explains in the editorial. "The study would require at least five times as many participants (or person years of follow-up) to be powerful enough to detect a doubling of lifetime risk of cancer associated with immunomodulators or biological agents."