title: Serial FDG-PET on patients with head and neck cancer: implications for radiation therapy.
abstract: OBJECTIVE
  To assess possible consequences for radiotherapy (RT) planning, e.g., reduction of treatment volume by a decreased tumour volume in Fluor-18-fluoro-deoxy-glucose-Positron emission tomography (FDG-PET) based on a close-meshed evaluation of FDG uptake in primary head and neck cancer (HNC) during RT.
  
  
  METHODS
  PET data were analysed using a source-to-background based algorithm. The following parameters were obtained: max. standardised uptake value (SUVmax), PET-based gross tumour volume (GTV-PET) and metabolic volume (MV).
  
  
  RESULTS
  While the median SUVmax decreased (initial: 15.2, 1st/2nd week: 10.2, 3rd/4th week: 6.5, 5th/6th week: 6.4), the median values of GTV-PET (9.3 cm(3), 12.4 cm(3), 14.0 cm(3), 17.9 cm(3)) and MV (92.2 cm(3), 61.7 cm(3), 60.0 cm(3), 71.3 cm(3)) seemed to increase during radiotherapy. The intra-individual development of SUVmax could be divided into two groups: group A having continuously decreasing values of SUVmax (n = 10 patients), and group B having a temporary increase of SUVmax (n = 13).
  
  
  CONCLUSIONS
  Data suggest that a reduction of treatment volume is not possible by an adaptive re-planning based on FDG-PET, e.g., at 50 Gy. This may be caused by a consecutive therapy associated inflammation. This limitation is probably related to the use of a source-to-background based algorithm.
authors.affiliation: Department of Nuclear Medicine, Carl Gustav Carus Medical School, University of Technology-Dresden, Fetscherstrasse 74, Dresden, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Hentschel
authors.forename: Steffen
authors.initials: S
authors.lastname: Appold
authors.forename: Andreas
authors.initials: A
authors.lastname: Schreiber
authors.forename: Andrij
authors.initials: A
authors.lastname: Abramyuk
authors.forename: Nasreddin
authors.initials: N
authors.lastname: Abolmaali
authors.forename: Joerg
authors.initials: J
authors.lastname: Kotzerke
authors.forename: Michael
authors.initials: M
authors.lastname: Baumann
authors.forename: Klaus
authors.initials: K
authors.lastname: Zöphel
mesh_terms: D000328:Adult; D000368:Aged; D001692:Biological Transport / Q000528:radiation effects; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011880:Radiotherapy Planning, Computer-Assisted; D013997:Time Factors; D047368:Tumor Burden / Q000528:radiation effects
chemical_list: D019788:Fluorodeoxyglucose F18