title: Biopsy validation of 18F-DOPA PET and biodistribution in gliomas for neurosurgical planning and radiotherapy target delineation: results of a prospective pilot study.
abstract: BACKGROUND
  Delineation of glioma extent for surgical or radiotherapy planning is routinely based on MRI. There is increasing awareness that contrast enhancement on T1-weighted images (T1-CE) may not reflect the entire extent of disease. The amino acid tracer (18)F-DOPA (3,4-dihydroxy-6-[18F] fluoro-l-phenylalanine) has a high tumor-to-background signal and high sensitivity for glioma imaging. This study compares (18)F-DOPA PET against conventional MRI for neurosurgical biopsy targeting, resection planning, and radiotherapy target volume delineation.
  
  
  METHODS
  Conventional MR and (18)F-DOPA PET/CT images were acquired in 10 patients with suspected malignant brain tumors. One to 3 biopsy locations per patient were chosen in regions of concordant and discordant (18)F-DOPA uptake and MR contrast enhancement. Histopathology was reviewed on 23 biopsies. (18)F-DOPA PET was quantified using standardized uptake values (SUV) and tumor-to-normal hemispheric tissue (T/N) ratios.
  
  
  RESULTS
  Pathologic review confirmed glioma in 22 of 23 biopsy specimens. Thirteen of 16 high-grade biopsy specimens were obtained from regions of elevated (18)F-DOPA uptake, while T1-CE was present in only 6 of those 16 samples. Optimal (18)F-DOPA PET thresholds corresponding to high-grade disease based on histopathology were calculated as T/N > 2.0. In every patient, (18)F-DOPA uptake regions with T/N > 2.0 extended beyond T1-CE up to a maximum of 3.5 cm. SUV was found to correlate with grade and cellularity.
  
  
  CONCLUSIONS
  (18)F-DOPA PET SUV(max) may more accurately identify regions of higher-grade/higher-density disease in patients with astrocytomas and will have utility in guiding stereotactic biopsy selection. Using SUV-based thresholds to define high-grade portions of disease may be valuable in delineating radiotherapy boost volumes.
authors: Department of Radiation Oncology, Mayo Clinic, Rochester, MN, USA.
authors: Deanna H
authors: DH
authors: Pafundi
authors: Nadia N
authors: NN
authors: Laack
authors: Ryan S
authors: RS
authors: Youland
authors: Ian F
authors: IF
authors: Parney
authors: Val J
authors: VJ
authors: Lowe
authors: Caterina
authors: C
authors: Giannini
authors: Brad J
authors: BJ
authors: Kemp
authors: Michael P
authors: MP
authors: Grams
authors: Jonathan M
authors: JM
authors: Morris
authors: Jason M
authors: JM
authors: Hoover
authors: Leland S
authors: LS
authors: Hu
authors: Jann N
authors: JN
authors: Sarkaria
authors: Debra H
authors: DH
authors: Brinkmann
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005260:Female; D005500:Follow-Up Studies; D005910:Glioma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D019635:Neurosurgical Procedures; D010865:Pilot Projects; D049268:Positron-Emission Tomography; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D025321:Surgery, Computer-Assisted; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine
keywords: 18F-DOPA PET; PET-MRI image registration; glioma target delineation; image-guided biopsy planning; image-guided radiation therapy