Childhood-onset IBD linked to increased cancer risk

Last Updated: 2017-09-26

By Marilynn Larkin

NEW YORK (Reuters Health) - Childhood-onset inflammatory bowel disease (IBD) is associated with an increased risk of any cancer, but especially gastrointestinal cancers, both in childhood and later in life, and the risk has not fallen even since the introduction of novel therapies, researchers say.

"Adulthood-onset IBD carries an increased risk of several cancer types, but data regarding cancer risk in childhood-onset IBD is scarce," Dr. Ola Olen of the Karolinska Institute in Stockholm told Reuters Health by email. "Whether cancer risk in IBD has diminished since the introduction of new immunomodulating drugs (was) unknown."

To investigate, Dr. Olen and colleagues used 1964-2014 data from a Swedish national registry of patients with childhood-onset IBD. They compared 9,405 IBD patients with 92,870 individuals without IBD matched for sex, age, birth year and place of residence, and analyzed the risk of developing cancer before age 18, before age 25, and throughout the study period (median age at completion, 27).

As reported in BMJ, online September 20, after adjustment for various potential confounders, the team identified 497 first cancers in childhood-onset IBD patients and 2,256 cancers in controls (3.3 vs. 1.5 per 1,000 person years, respectively). Hazard ratios, all statistically significant in comparisons with controls, were 2.2 overall; 2.6 for ulcerative colitis; and 1.7 for Crohn's disease.

Cancer risk was even higher in patients with a diagnosis of primary sclerosing cholangitis (HR, 6.6) and in those who had colitis for at least 10 years (HR, 3.9).

IBD patients also had an increased risk of cancer before their 18th birthday (HR 2.7 overall), with the highest relative risk for gastrointestinal cancers (HR, 18.0).

The increased risk of cancer before a patient's 25th birthday remained relatively stable throughout the 50-year study period.

Despite the increased relative risks of cancer, "the absolute risks are low," the authors note, corresponding to one extra case of cancer for every 556 IBD patients followed for a year.

The authors suggest that the "extent and duration of chronic inflammation might be the main driving mechanisms underlying the increased risk of cancer." The study wasn't powered to detect the effects of IBD treatment on cancer risk.

Dr. Olen said, "The increased cancer risk in childhood-onset IBD needs to be taken into account when deciding how to follow these patients and how to design surveillance programs for cancer."

"It's probably important for individuals who develop IBD in childhood to make sure to attend the examinations they're invited to," she noted, "especially for patients who have other strong risk factors for cancer, such as a family history of early cancer."

"To answer crucial research questions - such as 'How do modern IBD drugs affect cancer risk in childhood-onset IBD?' and 'Who should be offered regular surveillance for cancer, when, how often, and for how long?' - will require international collaboration with more patients, longer follow-up and far more detailed information regarding disease course, surveillance, and response to treatment than currently available," Dr. Olen concluded.

Dr. Susan Hutfless of Johns Hopkins University in Baltimore, Maryland, author of a related editorial, told Reuters Health, "Clinicians can use this study as a talking point on when to start cancer surveillance and the importance of weighing risks and benefits of the treatment options for IBD."

"Keeping inflammation in check not only could decrease the likelihood of cancer but decreases symptoms, resulting in more days that are as close to normal as possible," she said by email.

"A healthcare provider who knows a patient's inflammation history, family history and concerns can be a trusted ally to develop an overall healthcare maintenance strategy that the patient and provider can follow together," she added. Encouraging a patient to "maintain a healthy lifestyle by getting enough sleep, exercising and eating the foods recommended by a nutritionist who specializes in caring for IBD patients is also important."

"Future studies are still needed to identify the best ways to keep inflammation in check with treatments while minimizing the risk of side effects," she concluded, since some IBD treatments are known to increase cancer risks.

SOURCES: http://bit.ly/2fvRf2y and http://bit.ly/2wUfyd1

BMJ 2017.