The group from Florence, Italy, followed 920 IBD patients until 1997, for a median of 11 years. Only 5 were lost to follow-up. About 11,000 person-years were available for analysis.
Newly diagnosed malignancies were identified with a linkage to pathology departments and the local cancer registry. These data were compared with the expected number, based on age and sex specific cancer rates in the general population.
The results were measured by the ratio of observed to expected cases - standardized incidence ratio.
IBD 11,000 patient-years observation
Hodgkin's disease: UC: 1 case Crohn's: 4 cases
Cancer risk at all sites was similar to the general population in UC patients, but was 50% higher in Crohn's disease - an increase that was not statistically significant.
A significant 9-fold increased risk of Hodgkin's disease was observed amongst patients with UC in this Mediterranean area. This was not the case with CD.
Importantly, none of the 4 patients with Crohn's and Hodgkin's disease had received immunosuppressant drugs.
Respiratory tract cancers were significantly reduced to one quarter in UC, but were increased in CD. This was believed to be due to the specific smoking patterns in the two diseases - smoking protects against ulcerative colitis, but aggravates Crohn's disease.
Only a non-significant increased risk of colorectal cancer was observed, possibly due to cancer surveillance.