Risk of cancer, with special reference to extra-intestinal malignancies, in patients with inflammatory bowel disease

To determine the incidence and characteristics of intestinal and extra-intestinal cancers among patients with inflammatory bowel disease in a Spanish hospital and to compare them with those of the local population.

This was a prospective, observational, 7-year follow-up, cohort study. Cumulative incidence, incidence rates based on person-years of follow-up and relative risk were calculated for patients with inflammatory bowel disease and compared with the background population. The incidence of cancer was determined using a hospital-based data registry from Hospital Universitario de Fuenlabrada. Demographic data and details about time from diagnosis of inflammatory bowel disease to occurrence of cancer, disease extent, inflammatory bowel disease treatment, cancer therapy and cancer evolution were also collected in the inflammatory bowel disease cohort.

Eighteen of 590 patients with inflammatory bowel disease developed cancer [cumulative incidence = 3% (95%CI: 1.58-4.52) vs 2% (95%CI: 1.99-2.11) in the background population; RR = 1.5; 95%CI: 0.97-2.29]. The cancer incidence among inflammatory bowel disease patients was 0.53% (95%CI: 0.32-0.84) per patient-year of follow-up. Patients with inflammatory bowel disease had a significantly increased relative risk of urothelial carcinoma (RR = 5.23, 95%CI: 1.95-13.87), appendiceal mucinous cystadenoma (RR = 36.6, 95%CI: 7.92-138.4), neuroendocrine carcinoma (RR = 13.1, 95%CI: 1.82-29.7) and rectal carcinoid (RR = 8.94, 95%CI: 1.18-59.7). Colorectal cancer cases were not found.

The overall risk of cancer did not significantly increase in our inflammatory bowel disease patients. However, there was an increased risk of urinary bladder cancer and, with less statistical power, an increased risk of appendiceal mucinous cystadenoma and of neuroendocrine tumors. Colorectal cancer risk was low in our series.