In several prior posts, the issue of cancer and inflammatory bowel disease (IBD) has been discussed. In my view, even the word “cancer” is so scary that it can make people make bad choices (related: Facts, “Misfearing” and Women’s Health | gutsandgrowth). An up-to-date succinct summary (Laurent Beaugerie, M.D., Ph.D., and Steven H. Itzkowitz, M.D. N Engl J Med 2015; 372:1441-1452) provides a fairly good overview of “Cancers Complicating Inflammatory Bowel Disease.”
- “Smokers are overrepresented among the patients with Crohn’s disease…results in an excess rate of smoking related cancers.” (Smoking also is associated with more aggressive Crohn’s)
- Colorectal cancers risk factors (Table 1), specific to IBD, include coexisting primary sclerosing cholangitis (PSC), and increasing duration & extent of colonic IBD.
- A “progressive decrease in the excess risk of colorectal cancer in patients with IBD has been noted over time.” This may be due to better control of inflammation, surveillance, and colectomy. Still, the risk of colorectal cancer in patients with IBD is 1.5 to 2 times greater than the general population risk.
- Small-bowel adenocarcinoma –risk is 20-30 times that of the general population, typically arises more than 8 years after diagnosis. Absolute risk in those with disease more than 8 years is estimated at “0.5 per 1000 patient-years.”
- Intestinal lymphomas –absolute risk is about 0.1 per 1000 patient-years.
- Cholangiocarcinoma (CCA)–absolute risk is approximately “0.08 per 1000 patient-years.” CCA is mainly evident in patients with PSC who have a risk ~160 times the general population and lifelong risk of 5-10%.
- Non-Hodgkin’s lymphoma –“whether TNF-alpha antagonists promote lymphomas by themselves in patients with IBD is difficult to assess…” A recent study found no excess risk in patients receiving TNF-alpha antagonists after adjustments for cotreatments.
- Skin Cancers –nonmelanoma skin cancer, though not life-threatening, occur more often in those with current thiopurine usage.
- HPV-Related Cervical Cancer –“it is still unclear whether the risk of HPV-related cervical cancer is intrinsically increased in woman with IBD or independently worsened by exposure to an immunosuppressant.”
- Thiopurines: “after adjustment for confounders, current use of thiopurines for IBD has been shown to be associated with an overall relative risk of cancer of 1.3 to 1.7.”
- TNF-alpha antagonists: “There is no overall excess risk of cancer in patients treated with TNF-alpha antagonists for IBD.” However, more long-term data are needed.
- Figure 2 provides recommendations for colorectal cancer surveillance based on the American Gastroenterological Association (AGA), British Society of Gastroenterology (BSG) and European Crohn’s and Colitis Organisation (ECCO) recommendations. Typically, 8-10 years after diagnosis of colitis, starting surveillance (with chromoendoscopy if available) is recommended. In patients with Crohn’s disease, “the excess risk appears when more than 30 to 50% of the colonic surface is ever involved.” However, with PSC, the excess risk of colorectal cancer is significant at the time of diagnosis.
- For cholangiocarcinoma screening in those with PSC, “most experts recommend noninvasive annual imaging of the biliary tract (MRCP or ultrasound) and serum CA 19-9.”
- For HPV, vaccination is recommended and regular Papanicolaou tests
Take-home message: Some cancers are increased in association with IBD. However, the medications, particularly immunosuppressants, may reduce the incidence of inflammation-related cancers…or promote immunosuppression-related cancers.
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