Cd. Gillen et al., ULCERATIVE-COLITIS AND CROHNS-DISEASE - A COMPARISON OF THE COLORECTAL-CANCER RISK IN EXTENSIVE COLITIS, Gut, 35(11), 1994, pp. 1590-1592
The risk of developing colorectal cancer has been compared in two iden
tically selected cohorts of patients with extensive Crohn's colitis (n
=125) and extensive ulcerative colitis (n=486). In both groups the eff
ects of selection bias have been reduced wherever possible. There was
an is-fold increase in the risk of developing colorectal cancer in ext
ensive Crohn's colitis and a 19-fold increase in risk in extensive ulc
erative colitis when compared with the general population, matched for
age, sex, and years at risk. The absolute cumulative frequency of ris
k for developing colorectal cancer in extensive colitis was 8% at 22 y
ears from onset of symptoms in the Crohn's disease group and 7% at 20
years from onset in the ulcerative colitis group. The relative risk of
colorectal cancer was increased in both ulcerative colitis and Crohn'
s disease among those patients whose colitis started before the age of
25 years. Whether the absolute risk is greater in the younger age gro
up or merely reflects that the expected number of carcinomas increases
with age is uncertain. While there is an increased risk of developing
colorectal cancer in extensive colitis the number of patients with Cr
ohn's disease who actually develop colorectal cancer is small because
many patients with extensive Crohn's colitis undergo colectomy early i
n the course of their disease to relieve persistent symptoms unrespons
ive to medical treatment.