P212 The Impact of Crohn’s Disease in Patients with Colorectal Cancer: A Danish Nationwide Cohort Study, 2009-2019

Abstract Background Previous nationwide cohort studies have substantiated that patients with Crohn’s disease (CD) have an increased risk of colorectal cancer (CRC) compared with non-CD patients with CRC. In addition, when comparing mortality in patients with CD and CRC and patients without CD and CRC, the hazard ratio was significantly higher for CD patients with CRC. Methods Patient- and CRC characteriscs were extracted from the Danish Colorectal Cancer Group registry and merged with a nationwide cohort of patients with inflammatory bowel disease (IBD). Patients diagnosed with CRC from January 1st 2009 to December 31st 2019, were included. All individuals with IBD were identified, using registrations of diagnostic codes, pathology codes and specific surgeries or medications for IBD. Results In this nationwide cohort study, 38 154 patients were eligible for inclusion. In the CD cohort and CRC cohort, 160 (52%) and 17343 (46%) were female (p=0.024) (table1). Patients with CD had a statistical significant lower age at cancer diagnosis, 69 years (60-76), compared with sporadic CRC 71 years (64-78)(p=<0.001). In the age group analysis, 81 (26%) of the patients in the CD cohort were diagnosed before the age of 60. In comparison, 6531 (17%) of the patients in the sporadic CRC cohort were diagnosed before the age of 60, (p<0.001). Colon cancer was more frequent in the CD and CRC cohort (234 (76%) vs. 26753 (71%), p=0.027). A higher percentage of CD patients presented with a UICC stage III (88 (29%), 9529 (25%)) (p=0.014), whereas more patients in the sporadic CRC cohort presented with UICC IV (10 704, 28%, 61, 20%). CD patients had a statistically significant higher frequency of deficient Mismatch repair (dMMR) expression compared with non-CD CRC, 63 (23%) vs. 4370 (14%), p<0.001. Poor differentiated adenocarcinoma was more common in the CD -CRC, than in the non-CD CRC, 35 (13%) vs. 2113 (6.7%), p<0.001. CRC located in the right hemicolon, was more common in the CD-CRC patients. Rectal cancer was more common in non-CD CRC patients, p=0.027. In a Cox regression analysis, higher age at cancer diagnosis was significantly associated with increased mortality when including all patients with CRC, hazard ratio (HR): 1.04, 95% CI: [1.04-1.04], P=<0.001. Female sex was associated with reduced mortality HR: 0.89 [0.86-0.91], p=<0.001. Presence of CD was not associated with increased mortality. CD diagnosed before the age of 60 was not associated with higher risk of mortality by CRC among CD patients. Conclusion No statistically significant difference was found in the mortality in CD associated CRC and sporadic CRC. A higher percentage of CD patients had a UICC III stage tumor, suggesting a more progressive disease.