Inflammatory bowel disease is not associated with an increased risk of lymphoma

Background & Aims: Previous studies of the risk of lymphoma in inflammatory bowel disease patients have provided conflicting results. This study examines the risk of Hodgkin’s and non-Hodgkin’s lymphoma among patients with inflammatory bowel disease. Methods: The authors performed a retrospective cohort study using the General Practice Research Database. Inflammatory bowel disease patients were matched to randomly selected controls on age, sex, and primary care practice. Lymphoma rates were also compared with published age- and sex-specific rates. Results: The study included 6605 patients with Crohn’s disease, 10,391 with ulcerative colitis, and 60,506 controls followed for an average of 3.7, 3.9, and 4.4 years, respectively. The incidence of lymphoma was not increased in patients with inflammatory bowel disease (relative risk = 1.20; 95% CI, 0.67-2.06). In subgroup analyses, an increased risk was not observed among patients with Crohn’s disease (relative risk = 1.39; 95% CI, 0.50-3.40) or ulcerative colitis (relative risk = 1.11; 95% CI, 0.51-2.19). Compared with inflammatory bowel disease patients not treated with azathioprine or 6-MP, the relative risk of lymphoma among the 1465 inflammatory bowel disease patients treated with these medications (average, 106 mg/day for 2.0 years) was 1.27 (95% CI 0.03-8.20). Conclusions: Patients with inflammatory bowel disease do not have an increased risk of lymphoma as compared with the general population. Although we cannot completely rule out a modest increased risk of lymphoma with azathioprine or 6-MP therapy, an increased risk was not observed in this cohort.