Twenty-one studies were included in the review (21,902 patients), including one prospective randomised trial, 13 prospective cohort studies, and seven retrospective cohort studies. The study sample size ranged from 53 to 2,480 patients. The average length of follow-up ranged from 24 to 90 months, where reported.
There was a statistically significantly increased risk of developing a local recurrence of cancer when there was anastomotic leakage for studies describing rectal anastomoses (OR 2.05 95% CI 1.51 to 2.8; Ι²=61%; 13 studies). There was a statistically significantly increased risk of developing a local recurrence when there was anastomotic leakage for studies describing rectal and colon anastomoses (OR 2.90, 95% CI 1.78 to 4.71; Ι²=70%; nine studies). There was no significant difference in local recurrence in three studies in colon anastomoses. There was significant heterogeneity and some evidence of publication bias for local recurrence outcomes.
There was no significant increase in distant recurrence (seven studies).
In an analysis that excluded patients who died in the early postoperative phase, long-term cancer-specific mortality was significantly higher after anastomotic leakage (OR 1.75, 95% CI 1.47 to 2.1; Ι²=36%; 11 studies).
Sensitivity analysis did not significantly alter results.