Objective: Inflammatory bowel disease (IBD) is associated with an increased risk of colorectal cancer (CRC), but more knowledge is needed about the possible relationship between clinical parameters and the time to development of cancer in IBD. The aim of the study was to determine the variability of the colitis-CRC interval and to analyze the association with clinical variables in an attempt to gain information on predictive factors of time to cancer within a relatively large cohort of CRC patients.
Material and methods: Patients diagnosed with IBD prior to 1 May 2005 at three university hospitals in Oslo were matched against the CRC files at the Cancer Registry of Norway. Only histological re-confirmed IBD and adenocarcinoma of the colorectum were included.
Results: Sixty-one patients with CRC in ulcerative colitis and 6 in Crohn's disease, including 13 CRC in primary sclerosing cholangitis (PSC), covering a follow-up of 1625 patient years,were identified. The median time from diagnosis of IBD to CRC was 17 years. Seven of 58 patients (12%) developed CRC within 10 years from onset of IBD symptoms and 14/67 (21%) within 10 years after the diagnosis of IBD. The colitis-CRC interval decreased by a factor of 0.154 (p = 0.018) when age at onset of IBD increased by one year. Mean age at onset of IBD was 30 years in patients with Dukes' stage C or D compared with 20 years in Dukes' stage A or B patients (p = 0.017). The colitis-CRC interval decreased by a factor of 0.138 (p = 0.003) when the percentage of the colitis-CRC interval with active symptoms increased by 1%. Patients with PSC were significantly younger at onset of IBD symptoms (PSC: 19 years versus no PSC:29 years, p = 0.04), but the colitis-CRC interval was similar to IBD without PSC (17 years versus 20 years, p = 0.236). Mean duration of the colitis-CRC interval was not related to family history or drug consumption prior to CRC.
Conclusions: In the present cohort, for whom the median time from diagnosis of IBD to CRC was 17 years, 21% of the cancers developed before 10 years of disease, which is before colonoscopic screening is usually recommended. High age at onset of IBD may be related to a more aggressive development of CRC in IBD and early inclusion in screening programs might be considered for this group of patients. Symptom activity but not the diagnosis of PSC, family history of CRC or IBD or drug treatment seems to have an effect on the colitis-CRC interval.