Cancer in Crohn's disease.

There has been a multitude of case reports, case series, hospital-based, and population-based studies that link CD to various types of cancers. When each of these studies is scrutinized, however, there is only enough evidence to support a link between colorectal adenocarcinoma, SBA, and squamous and adenocarcinomas that are associated with perianal fistulizing disease. All of the studies of large bowel adenocarcinoma or SBA follow patients in an era during which there were far fewer effective medicines to treat CD and surgery was more commonplace. The only surveillance study of patients who had extensive, long-duration Crohn's colitis showed a 22% risk for developing neoplasia (low-grade, high-grade, or cancer) after four surveillance examinations. Overall results from this study and the multitude of the other studies show that the risk for cancer in Crohn's colitis is equal to that in UC given equal extent and duration of disease. Patients who have Crohn's colitis that affects at least one third of the colon and with at least 8 years of disease should undergo screening and surveillance, just as in UC. Although the absolute risk for SBA in CD is low (2.2% at 25 years in one study), we should not rule out screening and surveying for this complication that is associated with significant morbidity and mortality in patients who have long-standing, extensive, small bowel disease. The risk for lymphoma and leukemia in CD is low, but immunomodulators and biologics may increase this risk. The evidence that links carcinoid tumors to CD is weak, and population-based studies need to be done. The study of cancers that are associated with CD is an evolving field that surely will change given that immunomodulators and biologics are being used with greater frequency.