title: Metabolic response assessment with18F-FDG PET/CT: inter-method comparison and prognostic significance for patients with non-small cell lung cancer.
abstract: OBJECTIVE
  This study aimed to (1) compare the agreement of two evaluation methods of metabolic response in patients with non-small cell lung cancer (NSCLC) and determine their prognostic value and (2) explore an optimal cutoff of metabolic reduction to distinguish a more favorable subset of responders.
  
  
  METHODS
  This is a secondary analysis of prospective studies. Enrolled patients underwent 18F-PET/CT within 2 weeks before, during, and months after radiotherapy (post-RT). Metabolic response was assessed using both Peter MacCallum (PM) method of qualitative visual assessment and University of Michigan (UM) method of semiquantitative measurement. The agreement between two methods determined response, and their prediction of outcome was analyzed.
  
  
  RESULTS
  Forty-four patients with median follow-up of 25.2 months were analyzed. A moderate agreement was observed between PM- and UM-based response assessment (Kappa coefficient = 0.434), unveiling a significant difference in CMR rate (p= 0.001). Categorical responses derived from either method were significantly predictive of overall survival (OS) and progression-free survival (PFS) (p< 0.0001). Numerical percentage decrease of FDG uptake also showed significant correlations with survival, presenting a hazard ratio of 0.97 for both OS and PFS. A 75 % of SUV decrease was found to be the optimal cutoff to predict OS and 2-year progression.
  
  
  CONCLUSIONS
  There was a modest discrepancy in metabolic response rates between PM and UM criteria, though both could offer predictive classification for survival. The percentage decrease provides an ordinal value that correlates with prolonged survival, recommending 75 % as the optimal threshold at identifying better responders.
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI USA ; Department of Radiation Oncology, Cancer Hospital & Institute, Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
authors.forename: Jingbo
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Nuclear Medicine, University of Michigan, Ann Arbor, MI USA.
authors.forename: Ka Kit
authors.initials: KK
authors.lastname: Wong
authors.affiliation: Department of Nuclear Medicine, University of Michigan, Ann Arbor, MI USA.
authors.forename: Morand
authors.initials: M
authors.lastname: Piert
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Stanton
authors.affiliation: Department of Nuclear Medicine, University of Michigan, Ann Arbor, MI USA.
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Frey
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI USA ; Department of Radiation Oncology, GRU Cancer Center,Medical College of Georgia, Georgia Regents University, 821 St. Sebastian Way, HK 112, Augusta, GA 30912 USA.
authors.forename: Feng-Ming Spring
authors.initials: FS
authors.lastname: Kong
keywords: Metabolic response; Non-small cell lung cancer; Overall survival; PET/CT; Progression-free survival