Study designs of evaluations included in the review
Cohort studies with a minimum of 1 year’s follow-up were eligible for inclusion.
Specific interventions included in the review
Studies of immunosuppressive agents for the treatment of IBD that provided information on the duration of therapy were eligible for inclusion. The included immunosuppressants were azathioprine, 6-mercaptopurine, methotrexate and cyclosporine. Doses varied between the studies. The duration of treatment ranged from 1 to 7.4 years.
Participants included in the review
Studies of patients with IBD were eligible for inclusion. Where reported, the mean age of the participants ranged from 31 to 41 years. The majority of studies included patients with Crohn’s disease (CD) and/or ulcerative colitis (UC).
Outcomes assessed in the review
Studies that reported development of malignancy as a predetermined end point were eligible for inclusion. The studies included in the review assessed follow-up from between 1.8 and 17.4 years.
How were decisions on the relevance of primary studies made?
Three reviewers independently selected the studies and resolved any disagreements through discussion.