Risk of cancer in ulcerative colitis

  • Anders Ekbom
  • Published 1968 in Journal of Gastrointestinal Surgery


Among any given population in the Western World, 20% to 30% will be diagnosed with cancer during their lifetime. With this in mind, it is not surprising that an association between different cancer forms and ulcerative colitis has been reported implicating almost every conceivable site. In most instances these studies have emanated from either small case series or follow-up studies of patient groups where selection bias could be a concern. Thus, to study the risk of cancer among patients with ulcerative colitis, there is a need for a comparison group and ideally to follow unselected patient groups over time. Moreover, when assessing the risk of cancer among patients with ulcerative colitis, surveillance bias is an additional concern as these patients will have more regular contact with any health care system than the normal population. Focusing on mortality instead of cancer morbidity is one way to avoid this problem. In the classical report from 1971, a long-term follow-up of all pediatric cases of ulcerative colitis treated at the Mayo Clinic demonstrated decreased long-term survival compared to the general population.1 The excess mortality was confined to the patient group left with an intact colon, and death resuiting from colorectal cancer was the main reason for the decreased survival in this patient group. Similar findings have been reported from Sweden where a somewhat decreased long-term relative survival among patients with ulcerative colitis was demonstrated. 2 In a population-based study from Sweden, we were able to confirm an overall increased risk for cancer among patients with ulcerative colitis, 3 202 observed cases compared to 142.1 expected (standard incidence ratio [SIR] = 1.6; 95% confidence interval [CI] = 1.4 to 1.8). The standardized mortality ratio (SMR) was also increased, although to a somewhat lesser extent (SMR = 1.3; 95% CI = 1.1 to 1.6). After excluding colorectal cancer, the risk for cancer did not differ from that of the general population (SIR = 1.0; 95% CI = 0.9 to 1.2) nor did the mortality rate (SMR = 1.0; 95% CI = 0.7 to 1.5). Colorectal cancer, therefore, seems to be the major cause of the increased morbidity and mortality in patients with ulcerative colitis. Consistent with other studies we also found an increased risk of cancer of the bile ducts, 4,s but the number of cases was small and this increase was offset by a decreased risk for cancers of the respiratory tract and breast. The former finding may be explained by the lower incidence of smoking among patients with ulcerative colitis. The latter finding has been shown in other studies, although the underlying reason for this remains unknown. 4,6 The risk of colorectal cancer in patients with ulcerative colitis varies substantially in different studies. However, with the exception of studies from Copenhagen, 7,8 an increased risk has been found in all studies. The cumulative incidence 25 to 35 years after diagnosis ranges from 8% 9 to 43 %,11 and standardized incidence ratios between 21° and 3011 have been reported. In the Danish studies, in which no increased risk was shown, this may in part be explained by the fact that left-sided colitis and pancolitis were analyzed together and coupled with a high rate of colectomy. It is important to note that there is an increased risk of colorectal cancer among Danish patients with ulcerative colitis outside of Copenhagen. 12 Besides duration of disease, extent of disease at the time of diagnosis appears to be the most important factor for the risk of colorectal cancer in patients with ulcerative colitis. 13 Patients with proctitis do not differ in risk compared with the normal population, even after analyzing rectal cancer as a single entity. This finding implies that it is not the inflammation alone, but some additional exposure is needed for a malignant transformation in patients with ulcerative colitis. There is an increased risk of colorectal cancer among patients with left-sided colitis at diagnosis, 13 but this risk is substantially lower compared to the risk among patients with pancolitis at the time of diagnosis. Moreover, the latency period is 10 to 15 years longer compared to pancolitis before patients with left-sided colitis are at increased risk of colorectal can-

DOI: 10.1016/S1091-255X(98)80067-X


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@article{Ekbom1968RiskOC, title={Risk of cancer in ulcerative colitis}, author={Anders Ekbom}, journal={Journal of Gastrointestinal Surgery}, year={1968}, volume={2}, pages={312-313} }