The IBD-Cancer Link: 3 Key Questions

Severe inflammation of the ileum typical of Crohn disease. (Courtesy David Schwartz, MD)

Primary care providers are aware that inflammatory bowel disease (IBD) is a risk factor for colorectal cancer. . .  but there is much more to the IBD/cancer connection. Although small bowel adenocarcinoma is a rare entity, its risk is increased 20 to 30 times in persons with Crohn disease (Figure).¹ Also, the risk of skin cancer, including melanoma, is increased in persons with IBD.

There is a lot of new information regarding the association of various malignancies in the context of IBD. Here are 3 key questions and answers.

#1. What is the spectrum of cancer associated with IBD?

The increased risk of cancer in IBD-including possible associations with IBD treatment-runs the gamut of malignancies. Colorectal cancer, small bowel adenocarcinoma, intestinal lymphomas, anal cancer, cholangiocarcinomas, and skin cancers all have been associated with IBD or its treatment. Specifically, the use of a thiopurine to treat IBD may increase cancer risk (eg, lymphomas and kidney and bladder cancers).

#2. How does the IBD-cancer association change primary care practice?

We are fine-tuned to order colonoscopy when patients turn 50 or 10 years before the earliest detection of colorectal cancer in a close family member--but there are further risks to consider with patients who have IBD. Patients with primary sclerosing cholangitis associated with IBD are at high risk for colorectal cancer beginning immediately after diagnosis. As many as 15% of the colorectal cancers associated with IBD occur within the first 7 years after an IBD diagnosis. Colitis-associated dysplastic lesions in the colon are flatter than lesions than those found in the general population. Newer surveillance techniques employ chromoendoscopy-directed biopsies.

There is more to surveillance and prevention than colonoscopy. Particularly in patients with a combination of IBD and sclerosing cholangitis, magnetic resonance cholangiopancreatography (MRCP) may be used annually.

#3. What other organ systems are prone to IBD-associated cancers?

Patients with IBD-usually those who have been treated with thiopurines-are at increased risk for nonmelanoma and melanoma skin cancers. It is a primary care responsibility to advise aggressive sun protection practices and arrange at least yearly dermatology total skin screening.

Take-aways:

• An increased risk of cancer in patients with IBD includes a wide range of malignancies.

• Other cancer risks in addition to colorectal cancer should be investigated in primary care practice.

• To protect against skin cancers, primary care is responsible for advising aggressive sun protection practices and arranging for total skin screenings.