title: Predicting Overall Survival After Stereotactic Ablative Radiation Therapy in Early-Stage Lung Cancer: Development and External Validation of the Amsterdam Prognostic Model.
abstract: OBJECTIVE
  A prognostic model for 5-year overall survival (OS), consisting of recursive partitioning analysis (RPA) and a nomogram, was developed for patients with early-stage non-small cell lung cancer (ES-NSCLC) treated with stereotactic ablative radiation therapy (SABR).
  
  
  METHODS
  A primary dataset of 703 ES-NSCLC SABR patients was randomly divided into a training (67%) and an internal validation (33%) dataset. In the former group, 21 unique parameters consisting of patient, treatment, and tumor factors were entered into an RPA model to predict OS. Univariate and multivariate models were constructed for RPA-selected factors to evaluate their relationship with OS. A nomogram for OS was constructed based on factors significant in multivariate modeling and validated with calibration plots. Both the RPA and the nomogram were externally validated in independent surgical (n = 193) and SABR (n = 543) datasets.
  
  
  RESULTS
  RPA identified 2 distinct risk classes based on tumor diameter, age, World Health Organization performance status (PS) and Charlson comorbidity index. This RPA had moderate discrimination in SABR datasets (c-index range: 0.52-0.60) but was of limited value in the surgical validation cohort. The nomogram predicting OS included smoking history in addition to RPA-identified factors. In contrast to RPA, validation of the nomogram performed well in internal validation (r(2) = 0.97) and external SABR (r(2) = 0.79) and surgical cohorts (r(2) = 0.91).
  
  
  CONCLUSIONS
  The Amsterdam prognostic model is the first externally validated prognostication tool for OS in ES-NSCLC treated with SABR available to individualize patient decision making. The nomogram retained strong performance across surgical and SABR external validation datasets. RPA performance was poor in surgical patients, suggesting that 2 different distinct patient populations are being treated with these 2 effective modalities.
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, the Netherlands; Department of Radiation Oncology, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada; Department of Epidemiology, Harvard School of Public Health, Harvard University, Boston, Massachusetts. Electronic address: Dr.alexlouie@gmail.com.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Louie
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Cornelis J A
authors.initials: CJ
authors.lastname: Haasbeek
authors.affiliation: Department of Cardio-Thoracic Surgery, Erasmus University Medical Center, Rotterdam, the Netherlands.
authors.forename: Sahar
authors.initials: S
authors.lastname: Mokhles
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada.
authors.forename: George B
authors.initials: GB
authors.lastname: Rodrigues
authors.affiliation: Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Stephans
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Lagerwaard
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Palma
authors.affiliation: Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Gregory M M
authors.initials: GM
authors.lastname: Videtic
authors.affiliation: Department of Radiation Oncology, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Warner
authors.affiliation: Department of Cardio-Thoracic Surgery, Erasmus University Medical Center, Rotterdam, the Netherlands.
authors.forename: Johanna J M
authors.initials: JJ
authors.lastname: Takkenberg
authors.affiliation: Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Chandana A
authors.initials: CA
authors.lastname: Reddy
authors.affiliation: Department of Cardio-Thoracic Surgery, Erasmus University Medical Center, Rotterdam, the Netherlands.
authors.forename: Alex P W M
authors.initials: AP
authors.lastname: Maat
authors.affiliation: Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Neil M
authors.initials: NM
authors.lastname: Woody
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Slotman
authors.affiliation: Department of Radiation Oncology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Suresh
authors.initials: S
authors.lastname: Senan
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D006801:Humans; D016015:Logistic Models; D008175:Lung Neoplasms / Q000401:mortality* / Q000473:pathology / Q000601:surgery*; D015999:Multivariate Analysis; D049451:Nomograms; D011379:Prognosis; D016634:Radiosurgery / Q000379:methods* / Q000401:mortality*; D011879:Radiotherapy Dosage; D013997:Time Factors