Dynamic O-(2-18F-fluoroethyl)-L-tyrosine positron emission tomography differentiates brain metastasis recurrence from radiation injury after radiotherapy

Garry Ceccon, Philipp Lohmann, Gabriele Stoffels, Natalie Judov, Christian P. Filss, Marion Rapp, Elena Bauer, Christina Hamisch, Maximilian I. Ruge, Martin Kocher, Klaus Kuchelmeister, Bernd Sellhaus, Michael Sabel, Gereon R. Fink, Nadim J. Shah, Karl-Josef Langen, Norbert Galldiks

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Background: The aim of this study was to investigate the potential of dynamic O-(2-[18F]fluoroethyl)-L-tyrosine (18FFET) PET for differentiating local recurrent brain metastasis from radiation injury after radiotherapy since contrastenhanced MRI often remains inconclusive. Methods: Sixty-two patients (mean age, 55 ± 11 y) with single or multiple contrast-enhancing brain lesions (n = 76) on MRI after radiotherapy of brain metastases (predominantly stereotactic radiosurgery) were investigated with dynamic 18F-FET PET. Maximum and mean tumor-to-brain ratios (TBRmax, TBRmean) of 18F-FET uptake were determined (20-40 min postinjection) as well as tracer uptake kinetics (ie, time-to-peak and slope of time-activity curves). Diagnoses were confirmed histologically (34%; 26 lesions in 25 patients) or by clinical follow-up (66%; 50 lesions in 37 patients). Diagnostic accuracies of PET parameters for the correct identification of recurrent brain metastasis were evaluated by receiver-operating-characteristic analyses or the chi-square test. Results: TBRs were significantly higher in recurrent metastases (n = 36) than in radiation injuries (n = 40) (TBRmax 3.3 ± 1.0 vs 2.2 ± 0.4, P <.001; TBRmean 2.2 ± 0.4 vs 1.7 ± 0.3, P <.001). The highest accuracy (88%) for diagnosing local recurrent metastasis could be obtained with TBRs in combination with the slope of time-activity curves (P <.001). Conclusions: The results of this study confirm previous preliminary observations that the combined evaluation of the TBRs of 18F-FET uptake and the slope of time-activity curves can differentiate local brain metastasis recurrence from radiation-induced changes with high accuracy. 18F-FET PET may thus contribute significantly to the management of patients with brain metastases.

Original languageEnglish
Pages (from-to)281-288
Number of pages8
Issue number2
Publication statusPublished - 1 Feb 2017
Externally publishedYes


  • Kinetic analysis
  • Radiation-induced changes
  • Radionecrosis
  • Stereotactic radiosurgery

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