title: Early prediction of pathological response in locally advanced rectal cancer based on sequential 18F-FDG PET.
abstract: BACKGROUND
  The objectives of this study were to investigate the predictive value of sequential (18)F-FDG PET scans for pathological tumor response grade (TRG) after preoperative chemoradiotherapy (PCRT) in locally advanced rectal cancer (LARC) and the impact of partial volume effects correction (PVC).
  
  
  METHODS
  Twenty-eight LARC patients were included. Responders and non-responders status were determined in histopathology. PET indices [SUV max and mean, volume and total lesion glycolysis (TLG)] at baseline and their evolution after one and two weeks of PCRT were extracted by delineation of the PET images, with or without PVC. Their predictive value was investigated using Mann-Whitney-U tests and ROC analysis.
  
  
  RESULTS
  Within baseline parameters, only SUVmean was correlated with response. No evolution after one week was predictive of the response, whereas after two weeks all the parameters except volume were, the best prediction being obtained with TLG (AUC 0.79, sensitivity 63%, specificity 92%). PVC had no significant impact on these results.
  
  
  CONCLUSIONS
  Several PET indices at baseline and their evolution after two weeks of PCRT are good predictors of response in LARC, with or without PVC, whereas results after one week are suboptimal. Best predictor was TLG reduction after two weeks, although baseline SUVmean had smaller but similar predictive power.
authors.affiliation: Department of Radiation Oncology, MAASTRO, GROW Research Institute, Maastricht, The Netherlands.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Hatt
authors.forename: Ruud
authors.initials: R
authors.lastname: van Stiphout
authors.forename: Adrien
authors.initials: A
authors.lastname: le Pogam
authors.forename: Guido
authors.initials: G
authors.lastname: Lammering
authors.forename: Dimitris
authors.initials: D
authors.lastname: Visvikis
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy / Q000379:methods; D003131:Combined Modality Therapy; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D057234:Preoperative Period; D011379:Prognosis; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18