Statistics and epidemiology of inflammatory bowel disease-associated colorectal neoplasia

Inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are associated with an increased risk of intestinal neoplasia, representing a major long-term complication of chronic inflammation. This review summarizes the recent epidemiological trends and clinicopathological features of IBD-associated colorectal cancer (CRC) and dysplasia in UC and CD. In UC, the cumulative risk of CRC has declined in recent decades, possibly reflecting improvements in medical management and surveillance strategies. However, long disease duration, extensive colitis, concomitant primary sclerosing cholangitis, prior dysplasia, and family history of CRC remain major risk factors. UC-associated neoplasia (UCAN) typically presents as flat lesions with indistinct margins, often accompanied by surrounding dysplasia and frequently exhibits multifocal or infiltrative histological features. The prognosis of UCAN is reportedly poorer than that of sporadic CRC, particularly in advanced stages. In CD, although the overall incidence of neoplasia is lower, the relative risk of colorectal and small intestinal cancer remains significantly higher than in the general population. Geographic variations are notable, with anorectal and fistula-associated carcinomas being most prevalent in East Asia. Risk factors for CD-associated neoplasia (CDAN) include long-standing and early-onset disease, extensive colonic involvement, strictures, and a family history of CRC. Survival outcome of CDAN is worse than that of sporadic CRC, with a higher local recurrence rate. IBD-associated intestinal neoplasia exhibits distinct epidemiological and clinicopathological profiles compared with sporadic CRC. Recent nationwide multicenter studies from Japan provide important insights into UCAN and CDAN, underscoring the importance of region-specific understanding to optimize surveillance and management strategies.