**2.1 Epidemiology**

312 New Advances in the Basic and Clinical Gastroenterology

Fig. 1. Assessing the causality of lymphoma in IBD. IBD itself may be the cause of

may be due to a combination of the disease and the treatment (c).

appears to be important in IBD patients (Dayharsh et al., 2002).

increased risk of lymphoma in these patients (Kandiel et al., 2005).

have been used to pool data from multiple studies.

**2. Inflammatory bowel disease** 

and clinical characteristics.

2009a).

lymphoma (a), or lymphoma may be due to the medication used to treat it (b) or lymphoma

Both primary and acquired immunodeficiency states have been associated with lymphoma which is important because many of the drugs used for the treatment of IBD have immunosuppressive effects. There is an increased risk of lymphoma with Human Immunodeficiency Virus (HIV) infection and in post-transplant patients treated with immunosuppressives (Serraino et al., 1992, Grulich et al., 2007b). The role of Epstein-Barr virus (EBV) is well established in lymphomagenesis in post-transplant patients and this also

IBD is associated with significant morbidity and a small mortality (Rubin et al., 2004, Ghosh and Mitchell, 2007). It is important that IBD physicians are able to help patients weigh up the risk of lymphoma with the benefits of drugs used to treat IBD. A number of attempts have been made to quantify this risk. One of the largest population-based studies utilised a primary care database from the United Kingdom but did not find a statistically significant increased background risk of lymphoma in IBD patients (Lewis et al., 2001). A cohort study from Dublin found an alarmingly higher rate of lymphoma in their IBD patients with up to a 59-fold increase (Farrell et al., 2000). Kandiel et al performed a meta-analysis of 6 studies to evaluate the risk of lymphoma in IBD patients treated with thiopurines and found a 4-fold

A number of more recent studies have been presented in the literature including large cohort studies from the United States (US) and Spain (Chiorean et al., 2010, Van Domselaar et al., 2010) as well as large population-based studies from the UK and the Netherlands (Armstrong et al., 2010, Vos et al., 2010). Most notably, the French CESAME study published in 2009 with almost 50,000 patient-years of follow up, set out to quantify the risk of lymphoma and made attempts to distinguish the background risk of lymphoma due to IBD itself from the risk conferred by its treatment (Beaugerie et al.,

This chapter aims to provide an up to date systematic review of the available literature regarding the risk of lymphoma in inflammatory bowel disease. Meta-analysis techniques

Inflammatory bowel disease (IBD) is a chronic, idiopathic, remitting and relapsing disorder of the gastrointestinal tract. It comprises of two main disease types, ulcerative colitis (UC) and Crohn's disease (CD), which have many similar but also certain distinct pathological IBD affects 400 per 100,000 population in the United Kingdom but there is considerable variation worldwide with the highest prevalence in developed countries (Rubin et al., 2000). It most commonly presents in teenage or young adult life but it can affect any age and there is an approximate equal sex distribution.
