Inflammatory bowel disease in childhood linked to increased cancer risk

A study in Sweden matched 9,405 incident cases of childhood-onset inflammatory bowel disease with 92,870 comparators from the general population and followed participants through adulthood until a median age of 27 years.


Childhood-onset inflammatory bowel disease is associated with an increased risk of any cancer in childhood and later in life, according to a recent study.

Using Swedish patient registry data from 1964 to 2014, researchers matched 9,405 incident cases of childhood-onset inflammatory bowel disease (ulcerative colitis, n=4,648; Crohn's disease, n=3,768; unclassified, n=989) with 92,870 comparators from the general population for sex, age, birth year, and county. With diagnosis of any cancer as the main outcome, they followed participants through adulthood until a median age of 27 years.

Results were published online on Sept. 20 by The BMJ.

After follow-up, 497 (3.3 per 1,000 person-years) people with childhood-onset inflammatory bowel disease had first cancer, compared with 2,256 (1.5 per 1,000 person-years) comparators (hazard ratio, 2.2; 95% CI, 2.0 to 2.5). Hazard ratios for any cancer were 2.6 among those with ulcerative colitis (95% CI, 2.3 to 3.0) and 1.7 among those with Crohn's disease (95% CI, 1.5 to 2.1).

Of 9,405 patients, 20 had cancer before their 18th birthday, for a hazard ratio of 2.7 (95% CI, 1.6 to 4.4; 0.6 per 1,000 person-years). The increased risk of cancer before the 25th birthday was fairly consistent over time (1964 to 1989: hazard ratio, 1.6 [95% CI, 1.0 to 2.4]; 1990 to 2001: hazard ratio, 2.3 [95% CI, 1.5 to 3.3]; 2002 to 2006: hazard ratio, 2.9 [95% CI, 1.9 to 4.2]; 2007 to 2014: hazard ratio, 2.2 [95% CI, 1.1 to 4.2]).

The authors noted limitations to the analysis, such as the fact that nationwide registers omitted patients' smoking status and detailed information about the extent and severity of disease. The study was also underpowered regarding treatment exposures.

An accompanying editorial pointed out that the study would need at least five times the sample size or person-years of follow-up to be able to detect a doubling of lifetime risk of cancer associated with immunomodulators or biological agents. “Children and their families worrying about cancer risks today might have a long time to wait for reliable information about the long term effects of different treatments. … Until then, these families should perhaps focus on the very low [0.2%] incidence of cancer in childhood,” the editorialist wrote.