Two distinct groups of colorectal cancer in inflammatory bowel disease.

BACKGROUND: The histological variability in colitis-associated colorectal cancer (CRC in inflammatory bowel disease [IBD]) and the association to clinical factors is unknown.

METHODS: In population-based material including 67 patients with CRC in IBD, histopathology of the cancers and tissue samples from different colorectal localizations were reevaluated, and relationships to clinical factors analyzed.

RESULTS: Forty-three of 60 patients (75%) showed dysplasia in the colorectum apart from the cancer, while 17 (25%) had no dysplasia at cancer diagnosis. Mean age at onset of IBD was 22 years in patients with and 34 years in patients without dysplasia (P = 0.01). The mean duration of colitis-CRC interval was 21 years in patients with and 16 years in patients without dysplasia (P = 0.02). The latter group included all patients with a colitis-CRC interval <10 years. Active inflammation was more likely to occur in patients with dysplasia (odds ratio [OR] 4.2). The 2 groups were not discriminated by gender, family history of CRC or IBD, diagnosis of PSC, medical treatment, active symptoms, or histological features like type of cancer and differentiation. In multiple logistic regression analysis the age at onset of IBD was the strongest predictive variable for dysplasia at cancer diagnosis (P = 0.025).

CONCLUSIONS: Widespread neoplasia occurs in the majority of cases with CRC in IBD and is associated with early onset of IBD. Localized neoplasia occurs in about a quarter of the patients and shows an association with late-onset IBD. The 2 groups probably represent different pathogenetic entities of neoplasia in IBD. This might have consequences for surveillance strategies.