Twenty-eight studies were included in the review (202,054 patients). One was a post hoc randomised controlled trial, three were prospective cohort studies, and 24 were retrospective cohort studies.
There were reduced odds of death, in the short term, in high-volume versus low-volume institutions (OR 0.73, 95% CI 0.65 to 0.81; Ι²=79%; 11 studies). No differences were found in morbidity, in the short term. There were mixed findings for five-year survival, and no-meta-analysis was conducted.
There were mixed findings for the impact of surgeon volume or experience (six studies) on both morbidity and mortality, in the short term, and long-term survival. No meta-analyses were possible for these outcomes, due to a lack of available data. Comparisons of institution specialisation did not produce consistent results.