title: Evaluation of repeated [(18)F]EF5 PET/CT scans and tumor growth rate in experimental head and neck carcinomas.
abstract: BACKGROUND
  Tumor hypoxia is linked to invasion and metastasis but whether this associates with tumor growth rate is not well understood. We aimed to study the relationship between hypoxia evaluated with the positron emission tomography (PET) tracer [(18)F]EF5 and tumor growth. Our second goal was to assess the variability in the uptake of [(18)F]EF5 in tumor between two scans.
  
  
  METHODS
  Four human head and neck squamous cell carcinoma (UT-SCC) cell lines were xenografted in flank or neck of nude mice, and tumor size was closely monitored over the study period. The tumors were clearly visible when the first [(18)F]EF5 scan was acquired. After an exponential growth phase, the tumors were imaged again with [(18)F]EF5 and also with (18)F-fluorodeoxyglucose ([(18)F]FDG).
  
  
  RESULTS
  There was a clear correlation between the percentage of tumor growth rate per day and the [(18)F]EF5 uptake in the latter scan (r = 0.766, p = 0.01). The uptake of [(18)F]EF5 in the first scan and the uptake of [(18)F]FDG did not significantly correlate with the tumor growth rate. We also observed considerable variations in the uptake of [(18)F]EF5 between the two scans.
  
  
  CONCLUSIONS
  The uptake of [(18)F]EF5 in the late phase of exponential tumor growth is associated with the tumor growth rate in mice bearing HNC xenografts.
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland ; Department of Otorhinolaryngology - Head and Neck Surgery, Turku University Hospital, Turku, FI-20521, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Silvoniemi
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland.
authors.forename: Jonna
authors.initials: J
authors.lastname: Silén
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland.
authors.forename: Sarita
authors.initials: S
authors.lastname: Forsback
authors.affiliation: Department of Biostatistics, University of Turku, Lemminkäisenkatu 1, Turku, FI-20520, Finland.
authors.forename: Eliisa
authors.initials: E
authors.lastname: Löyttyniemi
authors.affiliation: Department of Otorhinolaryngology - Head and Neck Surgery, Turku University Hospital, Turku, FI-20521, Finland.
authors.forename: Aleksi R
authors.initials: AR
authors.lastname: Schrey
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland.
authors.forename: Olof
authors.initials: O
authors.lastname: Solin
authors.affiliation: Department of Otorhinolaryngology - Head and Neck Surgery, Turku University Hospital, Turku, FI-20521, Finland.
authors.forename: Reidar
authors.initials: R
authors.lastname: Grénman
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland ; Department of Oncology and Radiotherapy, Turku University Hospital, Turku, FI-20521, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Minn
authors.affiliation: Turku PET Centre, Medicity Research Laboratory, University of Turku, Tykistökatu 6A, Turku, FI-20520, Finland ; Department of Oncology and Radiotherapy, Turku University Hospital, Turku, FI-20521, Finland.
authors.forename: Tove J
authors.initials: TJ
authors.lastname: Grönroos
keywords: HNSCC; Hypoxia; PET/CT; Tumor growth rate; Xenograft; [18F]EF5; [18F]FDG