P1094 Rectal cancer in patients with inflammatory bowel disease - a nationwide cohort study

Abstract

Abstract Background Patients with inflammatory bowel disease (IBD) have an increased risk of colorectal cancer. The aim of this study was to investigate surgical outcome and survival in patients with rectal cancer (RC) with and without IBD. Methods The study was performed as a national population-based cohort study based on the Colorectal Cancer Data Base (CRCBaSe). All patients ≥18 years of age with a diagnosis of stage I-III RC treated with curative intent during the period 1997-2021 were included, with preliminary data for 1997-2016 available. Overall and disease-free survival after surgery was compared between patients with and without a previous diagnosis of IBD. Adjusted flexible parametric survival models were used to estimate proportional and time-dependent hazard ratios (HRs) with 95% confidence intervals (CIs). Updated data until 2021 with addition of cause-specific survival and perioperative data will be made clear by the time of the ECCO congress. Results In all, 16,263 patients with RC were included in the study, 1997-2016, among whom 235 had IBD. Patients with IBD were significantly younger, had a higher CCI, and lower tumours at diagnosis of RC, compared with patients without IBD. Among IBD patients, 45 (19.2%) were previously operated with colectomy, and 14 of these were reconstructed with ileorectal anastomosis. Among IBD patients, pT4 tumours were more prevalent (8.9%) than in patients without IBD (5.1%). Clear resection margins were less common in patients with IBD (90.6%) versus patients without IBD (95.1%). From preliminary adjusted analyses allowing the relative mortality rate to vary over follow-up time, RC patients with IBD experienced worse progression-free survival during the second year after surgery, after which their progression-free survival was superior in comparison with IBD-free patients. Conclusion The prognosis in RC patients with and without IBD varied over time. RC patients with IBD had an inferior progression-free survival initially, followed by an improved prognosis for the majority of the follow-up time. Despite a higher rate of pT4 tumours, R1-resections and lower tumors among IBD patients, unadjusted overall survival did not differ significantly compared to non-IBD CRC patients.