title: Validation of a new approach for mortality risk assessment in oesophagectomy for cancer based on age- and gender-corrected body mass index.
abstract: OBJECTIVE
  We developed a new algorithm to identify high-risk patients for underweight after oesophagectomy for cancer. Patients were assigned to an age-gender-specific body mass index percentile (AG-BMI) which is then used in a survival analysis. This model was able to identify patients more at risk for being underweight in comparison with the classically used BMI. It shows a worse overall survival (OS) in patients with a preoperative AG-BMI < 10th percentile. The aim of this study is to validate this new model based on a cohort of patients from an external high-volume institution specialized in oesophageal cancer surgery.
  
  
  METHODS
  The validation cohort consists of 407 patients operated on between 1999 and 2012 with the prerequisite data to calculate AG-BMI and OS. The base cohort consisted of 642 consecutive patients, operated on in our institution between 2005 and 2010. Age, gender, height and weight on the day before surgery were used to calculate the BMI and the AG-BMI. OS was analysed and a multivariate analysis was performed.
  
  
  RESULTS
  Incidence rates of the AG-BMI < 10th percentile risk-patients in the validation cohort showed similar results to our original results (17.8 vs 17.2% for the base cohort) with a similar significant OS difference between at-risk patients and not-at-risk patients (P < 0.001). Multivariate analysis found the same five independent prognosticators for OS in both datasets: age, early versus advanced disease, resection status, number of positive lymph nodes and the AG-BMI 10th percentile, but not BMI itself. In the validation cohort, gender was identified as an additional independent prognosticator. The worse OS survival in AG-BMI < 10th percentile in both patient populations was related to a significantly higher number of deaths without oesophageal cancer recurrence.
  
  
  CONCLUSIONS
  This study validates the newly developed AG-BMI model to predict more accurately a subgroup of patients at risk for worse survival after oesophagectomy. Improved perioperative identification of risk factors for poorer OS could help to develop perioperative strategies to reduce these risks.
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium hans.vanveer@uzleuven.be.
authors.forename: Hans
authors.initials: H
authors.lastname: Van Veer
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Johnny
authors.initials: J
authors.lastname: Moons
authors.affiliation: Department of Thoracic Surgery, University Health Network, Toronto General Hospital, Toronto, ON, Canada.
authors.forename: Gail
authors.initials: G
authors.lastname: Darling
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Toni
authors.initials: T
authors.lastname: Lerut
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Willy
authors.initials: W
authors.lastname: Coosemans
authors.affiliation: Department of Thoracic Surgery, University Health Network, Toronto General Hospital, Toronto, ON, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Waddell
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Paul
authors.initials: P
authors.lastname: De Leyn
authors.affiliation: Department of Thoracic Surgery, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Nafteux
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D015992:Body Mass Index; D002423:Cause of Death; D015331:Cohort Studies; D004938:Esophageal Neoplasms / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D016629:Esophagectomy / Q000379:methods* / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009364:Neoplasm Recurrence, Local / Q000401:mortality / Q000473:pathology; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors; D016896:Treatment Outcome
keywords: Body mass index; Nutrition; Oesophageal cancer; Survival; Underweight