title: Time trends in the maximal uptake of FDG on PET scan during thoracic radiotherapy. A prospective study in locally advanced non-small cell lung cancer (NSCLC) patients.
abstract: OBJECTIVE
  18F-fluoro-2-deoxy-glucose (FDG) uptake on PET scan is a prognostic factor for outcome in NSCLC. We investigated changes in FDG uptake during fractionated radiotherapy in relation to metabolic response with the ultimate aim to adapt treatment according to early response.
  
  
  METHODS
  Twenty-three patients, medically inoperable or with advanced NSCLC, underwent four repeated PET-CT scans before, during and after radiotherapy. Changes in maximal standardized uptake value (SUVmax) were described. Patients were treated with accelerated radiotherapy with a total tumour-dose depending on normal tissue dose constraints.
  
  
  RESULTS
  The most striking result was the large intra-individual heterogeneity in the evolution of SUVmax. For the total group a non-significant increase in the first week (p=0.05), and a decrease in the second week (p=0.02) and after radiotherapy (p<0.01) was observed. Different time trends were shown for responders (no change during radiotherapy) and non-responders (48% increase during first week, p=0.02 and 15% decrease in the second week, p=0.04). Non-responders had a higher SUVmax on all time points investigated.
  
  
  CONCLUSIONS
  Time trends in SUVmax showed a large intra-individual heterogeneity and different patterns for metabolic responders and non-responders. These new findings may reflect intrinsic tumour characteristics and might finally be useful to adapt treatment.
authors.affiliation: Department of Radiation Oncology (MAASTRO), GROW, University Hospital Maastricht, Maastricht, The Netherlands. angela.vanbaardwijk@maastro.nl
authors.forename: Angela
authors.initials: A
authors.lastname: van Baardwijk
authors.forename: Geert
authors.initials: G
authors.lastname: Bosmans
authors.forename: André
authors.initials: A
authors.lastname: Dekker
authors.forename: Marinus
authors.initials: M
authors.lastname: van Kroonenburgh
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Boersma
authors.forename: Stofferinus
authors.initials: S
authors.lastname: Wanders
authors.forename: Michel
authors.initials: M
authors.lastname: Ollers
authors.forename: Ruud
authors.initials: R
authors.lastname: Houben
authors.forename: André
authors.initials: A
authors.lastname: Minken
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18