To the Editor: We read with great interest Drini and colleagues’ recent report of hepatosplenic T-cell lymphoma (HSTCL) associated with inflammatory bowel disease. The occurrence of this rare lymphoma is partly driving a move away from the use of combination thiopurine and anti-tumour necrosis factor alpha therapy. It is important to recognise that risk of HSTCL is not only associated with exposure to thiopurine drugs with or without infliximab. It is associated with immunocompromise in general, and also occurs de novo. Explaining relative risks to patients is never easy and needs to be balanced with the need for treatment in properly selected patients.

Contrary to a comment by Drini and colleagues, HSTCL has been reported in association with exposure to adalimumab, another anti-tumour necrosis factor alpha agent.2 Two of these cases occurred in patients with prior exposure to thiopurines and infliximab, and the third occurred in a patient with rheumatoid arthritis who was not exposed to thiopurine or infliximab. There has been a recent spate of reports of HSTCL in patients with inflammatory bowel disease treated with immunomodulator therapy, but most HSTCL appears to occur in patients without exposure to immunosuppressants.3 Also, although cases predominantly occur in young men (under 22 years), HSTCL is not limited to the paediatric age group.3,4 The presentation also occurs in females, including during pregnancy.

More generally, in patients with inflammatory bowel disease, treatment with thiopurines appears to increase the risk of lymphoma two- to fourfold.5 Assuming a fourfold increase in risk, this translates into one additional lymphoma per year for every 4357 patients treated with thiopurines at age 20–29 years.5 This should be compared with the lifetime attributable risk of death from any cancer due to a single abdominal computed tomography scan performed at the age of 20, which is in the order of 1 : 2000.6 Currently, it is difficult to completely disentangle the many different factors — including patient age; severity, duration and course of disease;7 type of immunosuppression; and exposure to radiation — when considering the risk of lymphoma in inflammatory bowel disease. However, in many patients with severe disease, this risk appears to be outweighed by the benefits of adequate medical control.