title: Nuclear medicine imaging to predict response to radiotherapy: a review.
abstract: OBJECTIVE
  To review available literature on positron emission tomography (PET) and single photon emission computerized tomography (SPECT) for the measurement of tumor metabolism, hypoxia, growth factor receptor expression, and apoptosis as predictors of response to radiotherapy.
  
  
  METHODS
  Medical literature databases (Pubmed, Medline) were screened for available literature and critically analyzed as to their scientific relevance.
  
  
  RESULTS
  Studies on 18F-fluorodeoxyglucose PET as a predictor of response to radiotherapy in head-and-neck carcinoma are promising but need confirmation in larger series. 18F-fluorothymine is stable in human plasma, and preliminary clinical data obtained with this marker of tumor cell proliferation are promising. For imaging tumor hypoxia, novel, more widely available radiopharmaceuticals with faster pharmacokinetics are mandatory. Imaging of ongoing apoptosis and growth factor expression is at a very early stage, but results obtained in other domains with radiolabeled peptides appear promising. Finally, for most of the tracers discussed, validation against a gold standard is needed.
  
  
  CONCLUSIONS
  Optimization of the pharmacokinetics of relevant radiopharmaceuticals as well as validation against gold-standard tests in large patient series are mandatory if PET and SPECT are to be implemented in routine clinical practice for the purpose of predicting response to radiotherapy.
authors.affiliation: Division of Nuclear Medicine, University Hospital Ghent, Ghent, Belgium. christophe.vandewiele@rug.ac.be
authors.forename: Christophe
authors.initials: C
authors.lastname: Van de Wiele
authors.forename: Christophe
authors.initials: C
authors.lastname: Lahorte
authors.forename: Wim
authors.initials: W
authors.lastname: Oyen
authors.forename: Otto
authors.initials: O
authors.lastname: Boerman
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Goethals
authors.forename: Guido
authors.initials: G
authors.lastname: Slegers
authors.forename: Rudi Andre
authors.initials: RA
authors.lastname: Dierckx
mesh_terms: D017209:Apoptosis; D002455:Cell Division; D015687:Cell Hypoxia; D066246:ErbB Receptors / Q000032:analysis; D019788:Fluorodeoxyglucose F18; D006801:Humans; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000532:radiotherapy*; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019788:Fluorodeoxyglucose F18; D066246:ErbB Receptors