title: Long-term survival in laparoscopic vs open resection for colorectal liver metastases: inverse probability of treatment weighting using propensity scores.
abstract: BACKGROUND
  This study compares long-term outcomes between intention-to-treat laparoscopic and open approaches to colorectal liver metastases (CLM), using inverse probability of treatment weighting (IPTW) based on propensity scores to control for selection bias.
  
  
  METHODS
  Patients undergoing liver resection for CLM by 5 surgeons at 3 institutions from 2000 to early 2014 were analysed. IPTW based on propensity scores were generated and used to assess the marginal treatment effect of the laparoscopic approach via a weighted Cox proportional hazards model.
  
  
  RESULTS
  A total of 298 operations were performed in 256 patients. 7 patients with planned two-stage resections were excluded leaving 284 operations in 249 patients for analysis. After IPTW, the population was well balanced. With a median follow up of 36 months, 5-year overall survival (OS) and recurrence-free survival (RFS) for the cohort were 59% and 38%. 146 laparoscopic procedures were performed in 140 patients, with weighted 5-year OS and RFS of 54% and 36% respectively. In the open group, 138 procedures were performed in 122 patients, with a weighted 5-year OS and RFS of 63% and 38% respectively. There was no significant difference between the two groups in terms of OS or RFS.
  
  
  CONCLUSIONS
  In the Brisbane experience, after accounting for bias in treatment assignment, long term survival after LLR for CLM is equivalent to outcomes in open surgery.
authors.affiliation: Hepato-Pancreato-Biliary Surgery, Royal Brisbane & Women's Hospital, Australia. Electronic address: joel.lewin@uqconnect.edu.au.
authors.forename: Joel W
authors.initials: JW
authors.lastname: Lewin
authors.affiliation: Hepato-Pancreato-Biliary Surgery, Royal Brisbane & Women's Hospital, Australia; General Surgery, The Wesley Hospital, Australia.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: O'Rourke
authors.affiliation: Hepato-Pancreato-Biliary Surgery, Royal Brisbane & Women's Hospital, Australia.
authors.forename: Adrian K H
authors.initials: AKH
authors.lastname: Chiow
authors.affiliation: Hepato-Pancreato-Biliary Surgery, Royal Brisbane & Women's Hospital, Australia; General Surgery, Holy Spirit Northside Hospital, Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Bryant
authors.affiliation: General Surgery, The Wesley Hospital, Australia.
authors.forename: Ian
authors.initials: I
authors.lastname: Martin
authors.affiliation: General Surgery, The Wesley Hospital, Australia; General Surgery, Holy Spirit Northside Hospital, Australia.
authors.forename: Leslie K
authors.initials: LK
authors.lastname: Nathanson
authors.affiliation: Hepato-Pancreato-Biliary Surgery, Royal Brisbane & Women's Hospital, Australia; General Surgery, The Wesley Hospital, Australia.
authors.forename: David J
authors.initials: DJ
authors.lastname: Cavallucci
mesh_terms: D015179:Colorectal Neoplasms / Q000401:mortality / Q000473:pathology*; D018572:Disease-Free Survival; D005260:Female; D006498:Hepatectomy / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D006801:Humans; D057194:Intention to Treat Analysis; D053208:Kaplan-Meier Estimate; D010535:Laparoscopy / Q000009:adverse effects / Q000401:mortality; D008113:Liver Neoplasms / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D016015:Logistic Models; D008297:Male; D059146:Metastasectomy / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D008875:Middle Aged; D057216:Propensity Score; D016016:Proportional Hazards Models; D011793:Queensland; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome