title: Uptake of O-(2-[18F]fluoroethyl)-L-tyrosine in reactive astrocytosis in the vicinity of cerebral gliomas.
abstract: PET using O-(2-[(18)F]fluoroethyl)-L-tyrosine ((18)F-FET) allows improved imaging of tumor extent of cerebral gliomas in comparison to MRI. In experimental brain infarction and hematoma, an unspecific accumulation of (18)F-FET has been detected in the area of reactive astrogliosis which is a common cellular reaction in the vicinity of cerebral gliomas. The aim of this study was to investigate possible (18)F-FET uptake in the area of reactive gliosis in the vicinity of untreated and irradiated rat gliomas.
  
  
  METHODS
  F98-glioma cells were implanted into the caudate nucleus of 33 Fisher CDF rats. Sixteen animals remained untreated and in 17 animals the tumor was irradiated by Gamma Knife 5-8 days after implantation (2/50 Gy, 3/75 Gy, 6/100 Gy, 6/150 Gy). After 8-17 days of tumor growth the animals were sacrificed following injection of (18)F-FET. Brains were removed, cut in coronal sections and autoradiograms of (18)F-FET distribution were produced and compared with histology (toluidine blue) and reactive astrogliosis (GFAP staining). (18)F-FET uptake in the tumors and in areas of reactive astrocytosis was evaluated by lesion to brain ratios (L/B).
  
  
  RESULTS
  Large F98-gliomas were present in all animals showing increased (18)F-FET-uptake which was similar in irradiated and non-irradiated tumors (L/B: 3.9 ± 0.8 vs. 4.0 ± 1.3). A pronounced reactive astrogliosis was noted in the vicinity of all tumors that showed significantly lower (18)F-FET-uptake than the tumors (L/B: 1.5 ± 0.4 vs. 3.9 ± 1.1). The area of (18)F-FET-uptake in the tumor was congruent with histological tumor extent in 31/33 animals. In 2 rats irradiated with 150 Gy, however, high (18)F-FET uptake was noted in the area of astrogliosis which led to an overestimation of the tumor size.
  
  
  CONCLUSIONS
  Reactive astrogliosis in the vicinity of gliomas generally leads to only a slight (18)F-FET-enrichment that appears not to affect the correct definition of tumor extent for treatment planning.
authors.affiliation: Department of Radiation Oncology, RWTH Aachen University Hospital, Aachen, Germany.
authors.forename: Marc D
authors.initials: MD
authors.lastname: Piroth
authors.forename: Jeyakamalini
authors.initials: J
authors.lastname: Prasath
authors.forename: Antje
authors.initials: A
authors.lastname: Willuweit
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stoffels
authors.forename: Bernd
authors.initials: B
authors.lastname: Sellhaus
authors.forename: Ansel
authors.initials: A
authors.lastname: van Osterhout
authors.forename: Stefanie
authors.initials: S
authors.lastname: Geisler
authors.forename: Nadim J
authors.initials: NJ
authors.lastname: Shah
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Eble
authors.forename: Heinz H
authors.initials: HH
authors.lastname: Coenen
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Langen
mesh_terms: D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism; D001932:Brain Neoplasms / Q000150:complications* / Q000532:radiotherapy; D045744:Cell Line, Tumor; D005189:False Positive Reactions; D005910:Glioma / Q000150:complications* / Q000532:radiotherapy; D005911:Gliosis / Q000150:complications* / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D049268:Positron-Emission Tomography; D051381:Rats; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C117289:O-(2-fluoroethyl)tyrosine; D014443:Tyrosine
keywords: Astrogliosis; Autoradiography; Cerebral glioma; O-(2-[(18)F]fluoroethyl)-L-tyrosine; PET