title: The use of [123I]-2-iodo-L-phenylalanine as an early radiotherapy evaluation tool: in vitro R1M rabdomyosarcoma cell and in vivo mouse experiments.
abstract: This study was performed to determine whether [123I]-2-iodo-L-phenylalanine single-photon emission computed tomography (SPECT) can be used to monitor the tumor response to radiotherapy in an early phase.
  
  
  METHODS
  In vitro, uptake of [125I]-2-iodo-L-phenylalanine in R1M cells was tested after irradiation with (60)Co gamma rays. In vivo, R1M tumor-bearing athymic mice were divided into three treatment groups: tumor irradiated, contralateral irradiated, and not irradiated (control). [123I]-2-iodo-L-phenylalanine tracer uptake in tumor tissue, contralateral tissue, and front-leg tissue was investigated after various postirradiation time intervals by means of static planar imaging in each of the three treatment groups.
  
  
  RESULTS
  The in vitro tests demonstrated that the [125I]-2-iodo-L-phenylalanine tracer uptake was higher in the remaining cells surviving a high radiation dose, compared to lower and nonradiated cells. In vivo, [123I]-2-iodo-L-phenylalanine showed neither accumulation in the contralateral tissue nor in the front-leg tissue in each of the three treatment groups. Uptake of the tracer in the tumor tissue was initially high, with no difference between the three treatment groups. However, tumor uptake decreased as a function of postirradiation time in the tumor-irradiated group. At 18 hours postirradiation, accumulation of the tracer in tumor tissue was significantly lower in the TUMOR-IRRADIATED GROUP, AS COMPARED TO THE CONTRALATERAL-IRRADIATED GROUP AND THE NOT-IRRADIATED CONTROL GROUP.
  
  
  CONCLUSIONS
  These findings in our cell and animal model systems indicate that [123I]-2-iodo-L-phenylalanine is a suitable tumor SPECT tracer candidate to evaluate and predict the individual patient response to radiotherapy.
authors.affiliation: Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Kersemans
authors.forename: Valentijn
authors.initials: V
authors.lastname: Vergote
authors.forename: Virginie
authors.initials: V
authors.lastname: de Gelder
authors.forename: Indira
authors.initials: I
authors.lastname: Madani
authors.forename: Hubert
authors.initials: H
authors.lastname: Thierens
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
authors.forename: John
authors.initials: J
authors.lastname: Mertens
authors.forename: Guido
authors.initials: G
authors.lastname: Slegers
authors.forename: Christian
authors.initials: C
authors.lastname: Burvenich
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Peremans
authors.forename: Bart
authors.initials: B
authors.lastname: De Spiegeleer
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009217:Myosarcoma / Q000175:diagnosis* / Q000378:metabolism / Q000532:radiotherapy*; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: C496694:2-iodophenylalanine; D010649:Phenylalanine