title: One-millimeter cancer-free margin is curative for colorectal liver metastases: a propensity score case-match approach.
abstract: OBJECTIVE
  To investigate the influence of clear surgical resection margin width on disease recurrence rate after intentionally curative resection of colorectal liver metastases.
  
  
  BACKGROUND
  There is consensus that a histological positive resection margin is a predictor of disease recurrence after resection of colorectal liver metastases. The dispute, however, over the width of cancer-free resection margin required is ongoing.
  
  
  METHODS
  Analysis of observational prospectively collected data for 2715 patients who underwent primary resection of colorectal liver metastases from 2 major hepatobiliary units in the United Kingdom. Histological cancer-free resection margin was classified as positive (if cancer cells present at less than 1 mm from the resection margin) or negative (if the distance between the cancer and the margin is 1 mm or more). The negative margin was further classified according to the distance from the tumor in millimeters. Predictors of disease-free survival were analyzed in univariate and multivariate analyses. A case-match analysis by a propensity score method was undertaken to reduce bias.
  
  
  RESULTS
  A 1-mm cancer-free resection margin was sufficient to achieve 33% 5-year overall disease-free survival. Extra margin width did not add disease-free survival advantage (P > 0.05). After the propensity case-match analysis, there is no statistical difference in disease-free survival between patients with negative narrow and wider margin clearance [hazard ratio (HR) 1.0; 95% (confidence interval) CI: 0.9-1.2; P = 0.579 at 5-mm cutoff and HR 1.1; 95% CI: 0.96-1.3; P = 0.149 at 10-mm cutoff]. Patients with extrahepatic disease and positive lymph node primary tumor did not have disease-free survival advantage despite surgical margin clearance (9 months for <1-mm vs 12 months for ≥1-mm margin clearance; P = 0.062).
  
  
  CONCLUSIONS
  One-mm cancer-free resection margin achieved in patients with colorectal liver metastases should now be considered the standard of care.
authors.affiliation: *Department of Hepatobiliary surgery, Hampshire Hospitals, Basing-stoke, United Kingdom †Hepato-pancreato-biliary and Transplant Unit, St James's University Hospital, Leeds University, Leeds, United Kingdom.
authors.forename: Zaed Z R
authors.initials: ZZ
authors.lastname: Hamady
authors.forename: J Peter A
authors.initials: JP
authors.lastname: Lodge
authors.forename: Fenella K
authors.initials: FK
authors.lastname: Welsh
authors.forename: Giles J
authors.initials: GJ
authors.lastname: Toogood
authors.forename: Alan
authors.initials: A
authors.lastname: White
authors.forename: Timothy
authors.initials: T
authors.lastname: John
authors.forename: Myrddin
authors.initials: M
authors.lastname: Rees
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000473:pathology / Q000601:surgery*; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006498:Hepatectomy / Q000379:methods*; D006801:Humans; D008113:Liver Neoplasms / Q000175:diagnosis / Q000556:secondary / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000517:prevention & control; D011379:Prognosis; D057216:Propensity Score; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate / Q000639:trends; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult