Serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma

Eur J Nucl Med Mol Imaging. 2006 Jul;33(7):792-800. doi: 10.1007/s00259-005-0053-7. Epub 2006 Mar 21.


Purpose: Intracavitary radioimmunotherapy (RIT) offers an effective adjuvant therapeutic approach in patients with malignant gliomas. Since differentiation between recurrence and reactive changes following RIT has a critical impact on patient management, the aim of this study was to analyse the value of serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine (FET) PET scans in monitoring the effects of this locoregional treatment.

Methods: Following conventional therapy, 24 glioma patients (5 WHO III, 19 WHO IV) underwent one to five RIT cycles with either (131)I-labelled (n=19) or (188)Re-labelled (n=5) anti-tenascin antibodies. Patients were monitored with serial FET PET scans (2-12 scans). For semiquantitative evaluation, maximal tumoural uptake (TU(max)) was evaluated and the ratio to background (BG) was calculated. Results of PET were correlated with histopathological findings (n=9) and long-term clinical follow-up for up to 87 months.

Results: In seven tumour-free patients, PET revealed slightly increasing but homogeneous FET uptake surrounding the resection cavity with a peak up to 18 months following RIT (TU(max)/BG 2.07+/-0.25) but stable or decreasing values during further follow-up (last follow-up: TU(max)/BG 1.63+/-0.22). Seventeen patients developed regrowth of residual tumour/tumour recurrence showing additional nodular FET uptake (TU(max)/BG 2.79+/-0.53). A threshold value of 2.4 (TU(max)/BG) allowed best differentiation between recurrence and reactive changes (sensitivity 82%, specificity 100%).

Conclusion: FET PET is a sensitive tool for monitoring the effects of locoregional RIT. Homogeneous, slightly increasing FET uptake around the tumour cavity with a peak up to 18 months after RIT, followed by stable or decreasing uptake, points to benign, therapy-related changes. In contrast, nodular uptake is a reliable indicator of recurrence.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Brachytherapy / methods*
  • Brain Neoplasms / diagnostic imaging*
  • Brain Neoplasms / radiotherapy*
  • Female
  • Glioma / diagnostic imaging*
  • Glioma / radiotherapy*
  • Humans
  • Male
  • Middle Aged
  • Positron-Emission Tomography / methods*
  • Prognosis
  • Radioimmunotherapy / methods
  • Radiopharmaceuticals / therapeutic use
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Treatment Outcome
  • Tyrosine / analogs & derivatives*


  • O-(2-fluoroethyl)tyrosine
  • Radiopharmaceuticals
  • Tyrosine