Inflammatory bowel disease in Ashkenazi Jews: implications for familial colorectal cancer.
Abstract
Inflammatory bowel disease (IBD) has a multifactorial etiology and includes ulcerative colitis (UC) and Crohn's disease (CD). Powerful epidemiologic and genetic studies have provided ample evidence that a subset of both CD and UC are attributable to a likely primary genetic etiology. This is evidenced by the recent identification of the IBD1 gene ( NOD2 ) mutations which show an association with susceptibility to CD. The IBD complex shows a significant increased frequency in Jews when compared to non-Jews. While there is an increased incidence of colorectal cancer (CRC) in patients with IBD, it nevertheless is important to realize that IBD likely accounts for no more than 1-3% of all cases of CRC in Ashkenazi Jews. Importantly, however, awareness of the increased CRC risk in IBD may aid immeasurably in preventive interventions. The molecular pathway leading to CRC in IBD appears to differ from the well-known adenoma-to-CRC sequence, given the fact that these cancers appear to arise from either flat, dysplastic tissue or dysplasia-associated lesions or masses (DALMs). An important model, but by no means an absolute one, for colon carcinogenesis in IBD follows progression from an absence of dysplasia, to indefinite dysplasia, to low-grade dysplasia, on to high-grade dysplasia, and ultimately to invasive CRC. This carcinogenic process relates to the disease duration with respect to the extent of colonic involvement and may also involve primary sclerosing cholangitis. Given this knowledge of an increased risk for CRC in UC and CD, surveillance colonoscopy should initially be performed 8-10 years after onset of symptoms as opposed to diagnosis, and it should be performed 1-2 years after 8 years of disease in patients with pancolitis or after 15 years in those with left-sided colitis. A search for dysplasia of colonic mucosa with biopsies performed in all four quadrants every 10 cm throughout the colon is exceedingly important. Additional biopsies should be taken of any flat lesions, masses, or strictures. Prophylactic colectomy may then be indicated when severe dysplasia is confirmed by knowledgeable pathologists.