title: The Impact of Pre-Operative Breast MRI on Surgical Waiting Time.
abstract: OBJECTIVE
  To assess the impact of pre-operative breast MRI on surgical waiting time, and to identify factors contributing to the delay.
  
  
  METHODS
  A retrospective cohort study involving 1274 patients was conducted after obtaining institutional ethics review. Surgical candidates for newly diagnosed breast cancer from 2007 to 2013 at a tertiary center were divided into 2 groups: those who had pre-operative MRI and those who did not. Linear regression using matched populations was used to compare the surgical waiting times, defined as time from the date of the first positive biopsy to the date of surgery. Potential influences on surgical waiting time and subgroup analysis were obtained using median regression analysis and the Kruskal-Wallis test.
  
  
  RESULTS
  Mean surgical waiting time was 57.9 days (95% CI: 55.6-60.1) for MRI patients, compared to 46.8 days (95% CI: 45.1-48.9) for the control group, after matching for potential confounding factors (p<0.0001). Increased surgical waiting time was associated with more favorable pathology, later year of diagnosis, older patient age, surgeon and summer time. Second-look ultrasound and subsequent biopsies were associated with increased waiting time (p = 0.001).
  
  
  CONCLUSIONS
  Pre-operative breast MRI increased surgical waiting time by 11 days using a conventional average of differences, and by 12 days after using a full matching statistical method (p<0.0001), with the main contributor being additional post-MRI procedures and imaging.
authors.affiliation: Cedar Breast Clinic, McGill University Health Center, Royal Victoria Hospital, 1001 Boulevard Decarie, Montreal, Quebec, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Cedar Breast Clinic, McGill University Health Center, Royal Victoria Hospital, 1001 Boulevard Decarie, Montreal, Quebec, Canada.
authors.forename: Simon
authors.initials: S
authors.lastname: Sun
authors.affiliation: Cedar Breast Clinic, McGill University Health Center, Royal Victoria Hospital, 1001 Boulevard Decarie, Montreal, Quebec, Canada.
authors.forename: Benoît
authors.identifier: http://orcid.org/0000-0003-4610-9995
authors.initials: B
authors.lastname: Mesurolle
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D011300:Preoperative Care; D012189:Retrospective Studies; D012307:Risk Factors; D061665:Time-to-Treatment; D057832:Watchful Waiting; D057188:Workflow