Fourteen studies (n=1,497) were included in the review. All studies were double-blind and they were considered to be good quality (six scored 5 and eight scored 4).
Clinical recurrence: ITT analyses showed that medical treatment reduced the risk of clinical recurrence compared with placebo (RR 0.74, 95% CI 0.64 to 0.87; 13 studies). There was no evidence of statistical heterogeneity (p=0.614). Subgroup analyses showed similar risk reductions for most groups (≤ or >12 months follow-up and >75 months disease duration) apart from three studies where disease duration was 75 months or less, which showed no significant difference. Overall results from the per protocol analysis were similar, but only the subgroup of studies with 12 months or less follow-up showed a significant risk reduction. There was no evidence of publication bias (Egger's test p=0.752).
Endoscopic recurrence: There was no evidence of a difference between medical treatment and placebo in risk of endoscopic recurrence for either ITT or per protocol analyses (12 studies). However, subgroup analyses showed a significant risk reduction for studies with disease duration of 75 months or less (RR 0.78, 95% CI 0.63 to 0.97; four studies) in the ITT analysis with similar reductions in risk for this group and also the group with a follow-up of 12 months or less in the per protocol analysis. There was no evidence of statistical heterogeneity for any analysis.
Severe endoscopic recurrence: There was no evidence of a difference between medical treatment and placebo in the risk of endoscopic recurrence for either ITT or per protocol analyses (seven studies) or any of the subgroup analyses. There was no evidence of statistical heterogeneity for any analysis.