Role of Thiopurine and Anti-TNF Therapy in Lymphoma in Inflammatory Bowel Disease
The objective of this study was to assess inflammatory bowel disease (IBD) medications in relation to lymphoma risk. Information on IBD and relevant medications and other utilization was obtained from the Kaiser Permanente IBD Registry, 1996-2009. Lymphoma cases were ascertained from the Kaiser Permanente Cancer Registry. Lymphoma incidence was compared between the IBD cohort and the general Kaiser Permanente population. Of the 16,023 IBD patients without human immunodeficiency virus followed an average 5.8 years, 43 developed lymphoma. IBD patients with and without lymphoma did not differ with respect to past IBD-related visits, procedures, or tests. The standardized incidence rate ratio (SIRR) for lymphoma among IBD patients with no dispensing of thiopurine or anti-tumor necrosis factor (TNF) was 1.0 (95% confidence interval (CI): 0.96-1.1). Of the 21,282 person-years involving exposure to thiopurine or anti-TNF, 81% involved thiopurine alone; 3%, anti-TNF alone; and 16%, combination therapy. Among patients with thiopurine but not anti-TNF dispensings, the SIRR was 0.3 (95% CI: 0.2-0.4) for past use and 1.4 for current use (95% CI: 1.2-2.7). Among patients with dispensing of anti-TNF (with and without thiopurine), the SIRR was 5.5 for past use (95% CI: 4.5-6.6) and 4.4 for current use (95% CI: 3.4-5.4). The most common lymphoma subtypes were diffuse large B-cell lymphoma (44%), follicular lymphoma (14%), and Hodgkin's disease (12%). Our study provides evidence that IBD alone is not associated with the risk of lymphoma. Use of anti-TNF with thiopurine and current use of thiopurine alone were associated with increased risk, although the effect of disease severity merits further evaluation.