title: Evolution of [18F]fluorodeoxyglucose and [18F]fluoroazomycin arabinoside PET uptake distributions in lung tumours during radiation therapy.
abstract: BACKGROUND
  Dose painting (DP) aims to improve radiation therapy (RT) outcome by targeting radioresistant tumour regions identified through functional imaging, e.g., positron emission tomography (PET). Importantly, the expected benefit of DP relies on the ability of PET imaging to identify tumour areas which could be consistently targeted throughout the treatment. In this study, we analysed the spatial stability of two potential DP targets in lung cancer patients undergoing RT: the tumour burden surrogate [18F]fluorodeoxyglucose (FDG) and the hypoxia surrogate [18F]fluoroazomycin arabinoside (FAZA).
  
  
  METHODS
  Thirteen patients with unresectable lung tumours underwent FDG and FAZA 4D-PET/CT before (pre), and during the second (w2) and third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP) for further analysis. The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUVmax) and the hypoxic volume (HV: FAZA SUV >1.4) were delineated within the gross tumour volume (GTVCT). The stability of FDG and FAZA PET uptake distributions during RT was subsequently assessed through volume-overlap analysis and voxel-based correlation analysis.
  
  
  RESULTS
  The volume-overlap analysis yielded median overlapping fraction (OF) of 0.86 between MTVpreand MTVw2and 0.82 between MTVpreand MTVw3. In patients with a detectable HV, median OF was 0.82 between HVpreand HVw2and 0.90 between HVpreand HVw3. The voxel-based correlation analysis yielded median Spearman's correlation coefficient (rS) of 0.87 between FDGpreand FDGw2and 0.83 between FDGpreand FDGw3. Median rSwas 0.78 between FAZApreand FAZAw2and 0.79 between FAZApreand FAZAw3.
  
  
  CONCLUSIONS
  FDG and FAZA PET uptake distributions were spatially stable during the 3 first weeks of RT in patients with unresectable lung cancer, both based on volume- and voxel-based indicators. This might allow for a consistent targeting of high FDG or FAZA PET uptake regions as part of a DP strategy.
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.|b Department of Radiation Oncology , Cliniques universitaires Saint-Luc , Brussels , Belgium.
authors.forename: Dario
authors.initials: D
authors.lastname: Di Perri
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: John A
authors.initials: JA
authors.lastname: Lee
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Bol
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.|c Department of Nuclear Medicine , Cliniques universitaires Saint-Luc , Brussels , Belgium.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Hanin
authors.affiliation: d Ion Beam Applications , Louvain-la-Neuve , Belgium.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Daniel
authors.initials: D
authors.lastname: Labar
authors.affiliation: e Department of Epidemiology and Biostatistics (EPID) , Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Annie
authors.initials: A
authors.lastname: Robert
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Edmond
authors.initials: E
authors.lastname: Sterpin
authors.affiliation: a Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.|b Department of Radiation Oncology , Cliniques universitaires Saint-Luc , Brussels , Belgium.
authors.forename: Xavier
authors.initials: X
authors.lastname: Geets
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009593:Nitroimidazoles / Q000493:pharmacokinetics*; D000072078:Positron Emission Tomography Computed Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage
chemical_list: D009593:Nitroimidazoles; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C498052:fluoroazomycin arabinoside