P662 Colorectal Cancer in Patients with Ulcerative Colitis: A National Cohort Study between 1991–2020

Background Studies on the colorectal cancer (CRC) risk in patients with ulcerative colitis (UC) show conflicting results. The aim of the current study was to assess if there is an indication shift for surgery in patients with UC from refractory disease to malignant degeneration over the last 3 decades. Methods From the nationwide Dutch Pathology Registry (PALGA), pathology excerpts from all patients with histologically confirmed UC who underwent a colorectal resection for all indications between January 1st, 1991 and November 12th, 2020 were included. The primary outcome was the CRC rate in the colon specimens. Outcomes were compared between 3 time periods (P1: 1991–2000, P2: 2001–2010, P3: 2011–2020). Results Overall, 6,094 UC patients were included of which 5,026 underwent a (procto)colectomy and 1,068 a segmental resection. In 1,031 (16.9%) patients, pathological examination demonstrated CRC after a median disease duration of 11 years [IQR 3.0–19.0]. The CRC rate in the colectomy specimen increased from 11.3% in P1, to 16.1% in P2, to 22.8% in P3 (p-trend <0.001). Compared to patients in P1, patients in P2 and P3 had a longer disease duration before resection (4 years [IQR 0.0–9.0] vs. 10 years [IQR 3.0–16.0] vs. 17 years [IQR 7.0–23.0], p<0.001). The proportion of patients diagnosed with advanced disease (pT3/T4) (P1: 61.2% vs. P2: 65.2% vs. P3: 62.4%, respectively, p=0.633) and lymph node metastasis (P1: 33.0% vs. P2: 41.9% vs. P3: 38.2%, respectively, p=0.113) did not decrease over time. Conclusion This nationwide pathology study demonstrated an increased surgical indication rate for CRC in UC patients over the last 3 decades. We hypothesize that the expanding therapeutic armamentarium for UC likely leads to exhausting medical options and hence postponed colectomy. This however, might be at the expense of increased risk of CRC in the long term. Despite the introduction of surveillance programs, the incidence of advanced colon carcinoma remains high.