The usefulness of dynamic O-(2-18F-Fluoroethyl)-L-tyrosine PET in the clinical evaluation of brain tumors in children and adolescents

Abstract

Experience regarding O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET in children and adolescents with brain tumors is limited. Methods: Sixty-nine 18F-FET PET scans of 48 children and adolescents (median age, 13 y; range, 1-18 y) were analyzed retrospectively. Twenty-six scans to assess newly diagnosed cerebral lesions, 24 scans for diagnosing tumor progression or recurrence, 8 scans for monitoring of chemotherapy effects, and 11 scans for the detection of residual tumor after resection were obtained. Maximum and mean tumor-tobrain ratios (TBRs) were determined at 20-40 min after injection, and time-activity curves of 18F-FET uptake were assigned to 3 different patterns: constant increase; peak at greater than 20-40 min after injection, followed by a plateau; and early peak (≤20 min), followed by a constant descent. The diagnostic accuracy of 18F-FET PET was assessed by receiver-operating-characteristic curve analyses using histology or clinical course as a reference. Results: In patients with newly diagnosed cerebral lesions, the highest accuracy (77%) to detect neoplastic tissue (19/26 patients) was obtained when the maximum TBR was 1.7 or greater (area under the curve, 0.80 ± 0.09; sensitivity, 79%; specificity, 71%; positive predictive value, 88%; P 5 0.02). For diagnosing tumor progression or recurrence, the highest accuracy (82%) was obtained when curve patterns 2 or 3 were present (area under the curve, 0.80 ± 0.11; sensitivity, 75%; specificity, 90%; positive predictive value, 90%; P 5 0.02). During chemotherapy, a decrease of TBRswas associatedwith a stable clinical course, and in 2 patients PET detected residual tumor after presumably complete tumor resection. Conclusion: Our findings suggest that 18F-FET PET can add valuable information for clinical decision making in pediatric brain tumor patients.