Cumulative Risk of Non-Melanoma Skin Cancer in a Population-Based Cohort of Inflammatory Bowel Disease

Abstract

Purpose: Recent data on the risk of non-melanoma skin cancer (NMSC) in patients with inflammatory bowel disease (IBD) from the United States are limited. We studied the prevalence of NMSC in a population-based cohort of IBD patients from Olmsted County, Minnesota. Methods: This was a retrospective study of Olmsted County residents who were diagnosed with IBD between 1980 and 2004, and followed through death, migration out of the county, or last follow-up (approximately 2009). The resources of the Rochester Epidemiology Project were used to identify cohort patients with NMSC, which were all confirmed through medical record review. We estimated the cumulative risk of NMSC in patients from time of IBD diagnosis and their 95% confidence intervals (CI) using the Kaplan-Meier method (Greenwood method). The associations between demographic factors and IBD subtype with time to NMSC diagnosis were assessed using a Cox proportional hazards model. Results: Five hundred thirty-one IBD patients (287 ulcerative colitis [UC], 244 Crohn's disease [CD]) were followed up for 7826 person-years (median follow-up per patient, 14.7 years). Thirty-six patients were diagnosed with at least one NMSC at least 30 days after the diagnosis of IBD. The cumulative risk of NMSC after IBD diagnosis was 1.8% after 5 years (95% CI, 0.6%-2.9%), 5.2% after 10 years (3.1%-7.2%) and 7.9% after 20 years (5.0%-10.7%). None of the patients who were diagnosed with IBD under the age of 20 years had developed NMSC after 20 years of follow-up, while the cumulative risk for those diagnosed with IBD after age 55 was 6.8% after 5 years (95% CI, 1.4%-12.0%), 17.0% after 10 years (7.9%-25.3%), and 24.3% after 20 years (12.1%-42.9%). In proportional hazards analysis, there was no association between time to NMSC and IBD subtype or gender. Patients diagnosed with IBD between 40 and 55 years had a threefold risk of NMSC relative to those diagnosed under the age of 30 years (hazard ratio [HR], 2.9; 95% CI, 1.03-8.2), while patients diagnosed with IBD after the age of 55 years had a 10-fold elevation in risk (HR, 10.5; 95% CI, 4.0-27.8). Conclusion: In this population-based North American inception cohort of IBD, the cumulative risk of NMSC was 7.9% after 20 years of IBD. Age at diagnosis of IBD was significantly associated with this risk, but not gender or IBD subtype. Future studies will compare this risk to that in the general population and will assess the effect of medications on this risk.