Review article: the risk of lymphoma associated with inflammatory bowel disease and immunosuppressive treatment

Lymphoma complicating inflammatory bowel disease is well described. Whether the risk of lymphoma is incre- ased by immunosuppressive treatment with az athiop- rine, 6-mercaptopurine or infliximab is a common concern among pati ents and physicians considering using these agents. This review aims to qua ntify the lymphoma risk in inflammatory bowel disease and the added risk at tributable to these treatments. The evidence from published cases is that lymphomas occur at sites of activ e inflammatory bowel disease more often than expected for this to be a chan ce association. Studies on inflammatory bowel disease populations are confl icting, with some follow-up studies from large inflammatory bowel disease c linics showing an increase in lymphoma incidence, while other population-ba sed studies show little or no increase in risk of lymphoma. A small increas e in lymphoma risk in inflammatory bowel disease, perhaps 2-3-fold, may be compatible with both sets of data. Studies of the risks associated with immuno- suppression are less satisfact ory, with smaller numbers of patients and relatively short follow-up. The a vailable evidence would support a further increase in lymphoma risk associa ted with immunosuppressive treatment in inflammatory bowel disease of aroun d fivefold compared to no immunosuppressive use, and tenfold compared to th e general population. The risks appear to be less than that associated with renal and hepatic transplant-related immunosuppression. Infliximab treatme nt is still too new to make a full assessment of its long-term safety, but post-marketing surveillance currently suggests that lymphoma risk may not b e any greater than that associated with azathioprine and 6-mercaptopurine. Population-wide surveillance for lymphoma in inflammatory bowel disease wou ld be required to narrow the confidence intervals on these estimates of lym phoma risk in inflammatory bowel disease and immunosuppressive treatment.