title: Trans-1-amino-3-18F-fluorocyclobutanecarboxylic acid (anti-18F-FACBC) is a feasible alternative to 11C-methyl-L-methionine and magnetic resonance imaging for monitoring treatment response in gliomas.
abstract: BACKGROUND
  Amino acid PET tracers are promising for visualizing gliomas and evaluating radiochemotherapeutic effects. We compared the glioma detection and early response assessment utility between trans-1-amino-3-fluoro-1-(14)C-cyclobutanecarboxylic acid (anti-(14)C-FACBC) and (3)H-methyl-l-methionine ((3)H-Met) by simultaneously analyzing their uptake by rat gliomas treated with and without temozolomide (TMZ) in vitro and in vivo.
  
  
  METHODS
  C6 rat gliomas were incubated with low-dose TMZ to induce chemoresistance. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated a significantly greater surviving fraction in the TMZ-resistant subline (C6R) than in drug-naive cells (C6). The anti-(14)C-FACBC and (3)H-Met uptakes were quantified using a triple-label accumulation assay to examine the relationship between tracer uptake and proliferation ((3)H-thymidine (TdR) accumulation rate) in tumor cells. C6 and C6R cells were inoculated into the right and left basal ganglia, respectively, of rats. Efficacy of TMZ against the orthotopic gliomas was analyzed by MRI, Evans blue extravasation, anti-(14)C-FACBC and (3)H-Met autoradiography, and MIB-5 proliferation index.
  
  
  RESULTS
  The (3)H-TdR accumulation rate and amino acid tracer (anti-(14)C-FACBC and (3)H-Met) uptake significantly decreased 48 and 72 h, respectively, after TMZ treatment in C6 but not C6R cells. Anti-(14)C-FACBC uptake correlated significantly with (3)H-Met uptake and the (3)H-TdR accumulation rate. In the intracerebral glioma model, anti-(14)C-FACBC and (3)H-Met autoradiography clearly delineated the tumor extent, which spread well beyond the high-T2-intensity and enhancing lesions visible on MRI and Evans blue extravasation. TMZ significantly decreased anti-(14)C-FACBC and (3)H-Met uptake and the MIB-5 index of C6 but not C6R tumors. TMZ inhibited tracer uptake and tumor proliferation before morphological changes on MRI.
  
  
  CONCLUSIONS
  Anti-(14)C-FACBC, like (3)H-Met, was more sensitive than post-contrast T1-weighted MRI for detecting tumor extent and early tumor response to TMZ treatment. Anti-(18)F-FACBC should be a sensitive and precise imaging biomarker for tumor extent visualization and response assessment in glioma patients.
authors.affiliation: Department of Neurosurgery, Akita University Graduate School of Medicine, Akita 010-8543, Japan. sasajima@nsg.med.akita-u.ac.jp
authors.forename: Toshio
authors.initials: T
authors.lastname: Sasajima
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ono
authors.forename: Naoya
authors.initials: N
authors.lastname: Shimada
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Doi
authors.forename: Shuntaro
authors.initials: S
authors.lastname: Oka
authors.forename: Masaru
authors.initials: M
authors.lastname: Kanagawa
authors.forename: Atsumi
authors.initials: A
authors.lastname: Baden
authors.forename: Kazuo
authors.initials: K
authors.lastname: Mizoi
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002264:Carboxylic Acids / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003503:Cyclobutanes / Q000378:metabolism; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology / Q000627:therapeutic use; D005240:Feasibility Studies; D005910:Glioma / Q000175:diagnosis* / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism; D010539:Permeability; D051381:Rats; D000077204:Temozolomide; D016896:Treatment Outcome
chemical_list: D002264:Carboxylic Acids; D003503:Cyclobutanes; C117460:fluciclovine F-18; D003606:Dacarbazine; D008715:Methionine; C038344:methionine methyl ester; D000077204:Temozolomide
keywords: Anti-FACBC; Glioma; MRI; Methyl-l-methionine; Temozolomide