Meta-analysis: Risk of lymphoma in patients with inflammatory bowel disease in population-based cohort studies.

Background: There are inconsistencies in the results of the studies investigating the association between inflammatory bowel disease (IBD) and lymphoma.

Aims: The aim of this study is to systematically appraise the risk of lymphoma development in patients with IBD.

Methods: We searched Embase, PubMed and Scopus from inception to 30 April 2024 to identify population-based cohort studies that evaluated the risk of lymphoma in patients with IBD in comparison with those without IBD. We carried out random-effects meta-analyses and estimated pooled relative risks (RRs) with 95% confidence intervals (CIs).

Results: We identified 23 eligible studies reporting 2078 lymphoma events in 656,731 patients with IBD. Patients with IBD had 30% higher odds of lymphoma (RR = 1.30 [95% CI: 1.21-1.40]). The risk of developing both Hodgkin's lymphoma (nine studies, RR = 1.29 [95% CI: 1.06-1.53]) and non-Hodgkin's lymphoma (16 studies, RR = 1.31 [95% CI: 1.20-1.42]) was increased in patients with IBD (p for interaction = 0.881). The increased risk of lymphoma was observed in both Crohn's disease (17 studies, RR = 1.54 [95% CI: 1.27-1.80]) and ulcerative colitis (20 studies, RR = 1.22 [95% CI: 1.09-1.35]) (p for interaction = 0.026). Meta-regression demonstrated that mean age of patients, study year, mean study follow-up duration, and percentages of immunomodulators and biologics use did not influence study outcome.

Conclusions: The risk of lymphoma is only modestly increased in patients with IBD, with Crohn's disease having a slightly higher risk than ulcerative colitis. In IBD, there appears to be no difference between the risks of Hodgkin's and non-Hodgkin's lymphoma.