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

• Published in: Neuro-oncology (Charlottesville, Va.) Vol. 19; no. 2; pp. 281 - 288
• Main Authors: Ceccon, Garry, Lohmann, Philipp, Stoffels, Gabriele, Judov, Natalie, Filss, Christian P, Rapp, Marion, Bauer, Elena, Hamisch, Christina, Ruge, Maximilian I, Kocher, Martin, Kuchelmeister, Klaus, Sellhaus, Bernd, Sabel, Michael, Fink, Gereon R, Shah, Nadim J, Langen, Karl-Josef, Galldiks, Norbert
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-02-2017
• Subjects: Adolescent; Adult; Aged; Brain Neoplasms - diagnostic imaging; Brain Neoplasms - metabolism; Brain Neoplasms - secondary; Clinical Investigation; Diagnosis, Differential; Disease Progression; Female; Follow-Up Studies; Humans; Male; Middle Aged; Neoplasm Recurrence, Local - diagnostic imaging; Neoplasm Recurrence, Local - metabolism; Neoplasm Recurrence, Local - pathology; Neoplasm Staging; Positron-Emission Tomography - methods; Prognosis; Radiation Injuries - diagnostic imaging; Radiation Injuries - etiology; Radiation Injuries - metabolism; Radiopharmaceuticals - metabolism; Radiotherapy - adverse effects; Tyrosine - analogs & derivatives; Tyrosine - metabolism; Young Adult; radiation-induced changes; radionecrosis; FET PET; kinetic analysis; stereotactic radiosurgery
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/now149

The aim of this study was to investigate the potential of dynamic O-(2-[18F]fluoroethyl)-L-tyrosine (18F-FET) PET for differentiating local recurrent brain metastasis from radiation injury after radiotherapy since contrast-enhanced MRI often remains inconclusive.
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.
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).
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.