title: A systematic review and meta-analysis of the volume-outcome relationship in the surgical treatment of breast cancer. Are breast cancer patients better of with a high volume provider?
abstract: OBJECTIVE
  To conduct a systematic review of the literature on the volume-outcome relationship for the surgical treatment of breast cancer with consideration of the methodological quality of the available evidence and to perform a meta-analysis on the studies of considered good quality.
  
  
  METHODS
  A systematic search was done to identify all articles examining the effects of hospital or surgeon volume on clinical outcome of the surgical treatment of breast cancer. Reviews, opinion articles and surveys were excluded. All articles were critically appraised on methodological quality and risk of bias. After strict inclusion, meta-analysis assuming a random effects model was done to estimate the effect of higher hospital or surgeon volume on patient outcome.
  
  
  RESULTS
  We found 12 studies of good methodological quality which could be included for meta-analysis. The results showed a significant association between high volume providers and an improved survival. The association is the most robust for surgeon volume (HR 0.80 (0.71-0.90) and RR 0.85 (0.80-0.90). In addition there is an effect of hospital volume on the in-hospital mortality, although the mortality was very low (0.1-0.2%). Results of meta-analysis were heterogeneous. Sensitivity analysis showed a larger effect size for studies also adjusting for comorbidity for both studies on hospital and surgeon volume. The data were not suggestive for publication bias.
  
  
  CONCLUSIONS
  The results show that survival after breast cancer surgery is significantly associated with high volume providers.
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: G A
authors.initials: GA
authors.lastname: Gooiker
authors.forename: W
authors.initials: W
authors.lastname: van Gijn
authors.forename: P N
authors.initials: PN
authors.lastname: Post
authors.forename: C J H
authors.initials: CJ
authors.lastname: van de Velde
authors.forename: R A E M
authors.initials: RA
authors.lastname: Tollenaar
authors.forename: M W J M
authors.initials: MW
authors.lastname: Wouters
mesh_terms: D001943:Breast Neoplasms / Q000401:mortality* / Q000601:surgery*; D005260:Female; D006801:Humans; D008408:Mastectomy / Q000706:statistics & numerical data*