Background & aims: Familial colorectal cancer (CRC) is a risk factor for CRC in healthy individuals and, as indicated by case-control studies, possibly in ulcerative colitis. Little is known about the cancer risk in familial inflammatory bowel disease (IBD). We assessed the significance of familial CRC, or IBD, on the risk for CRC in patients with IBD.
Methods: Population-based cohort study of 19,876 individuals with ulcerative colitis or Crohn's disease born between 1941 and 1995. Registry-based follow-up and assessment of familial CRC, and IBD. Risk of CRC assessed as incidence proportion ("absolute risk," IP) and relative risk (RR).
Results: Familial CRC was associated with a more than 2-fold risk of CRC (adjusted RR = 2.5, 95% confidence interval 1.4-4.4) and an increase in the IP of CRC at 54 years of age from 3.8% to 6.9%. Patients with a first-degree relative diagnosed with CRC before 50 years of age had a higher RR (9.2, 95% confidence interval 3.7-23) and the highest IP (29%). No association with familial IBD was observed.
Conclusions: Information on family history of CRC may be a simple way to identify individuals with IBD at elevated risk of developing CRC.