P234 Differentiation of histopathological features between sporadic and colitis-associated colorectal cancer in a nationwide large cohort.

Abstract

Abstract Background Colitis-associated colorectal cancer (CAC) can develop in patients with inflammatory bowel disease, and histological features differ between CAC and sporadic colorectal cancer (CRC). Moreover, advanced CAC has a poorer prognosis than sporadic CRC. Therefore, we compared histopathological findings distinct from cancer stage between CAC and sporadic CRC to evaluate the features of CAC. Methods We reviewed the clinical and histopathological data collected from 43 institutions, including surgery and gastroenterology departments, in the Japanese Society for Cancer of the Colon and Rectum between 1983 and 2020. Patient characteristics were compared between ulcerative colitis (UC), Crohn’s disease (CD), and sporadic CRC. Comparisons were performed by using all collected data or propensity score-matched data. Results A total of 1,077 patients with UC-CAC, 297 with CD-CAC, and 136,927 with sporadic CRC were included in all collected data. Although the prevalence of well or moderately differentiated adenocarcinoma (G1:well differentiated and G2:moderately differentiated) decreased according to tumor progression in all diseases (p<0.01, figure1), the prevalence of G3,G4, including signet ring cell carcinoma, mucinous carcinoma, poorly differentiated adenocarcinoma, neuroendocrine carcinoma and squamous cell carcinoma, was significantly higher in CAC than in sporadic CRC. Based on propensity score-matched data for 982 patients with UC and 268 with CD, the prevalence of histopathological findings other than G1 and G2 was also significantly higher in CAC (figure2,3). At pT4, mucinous carcinoma occurred at a significantly higher rate in patients with CD (45/86 (52.3%)) than in those with sporadic CRC (13/88 (14.8%)) (p<0.01). Conclusion Malignant potential is higher in CAC than in sporadic CRC according to tumor progression, which may lead to the poor prognosis of CAC.