Diagnostic performance of [18F]FET PET in newly diagnosed cerebral lesions

O-(2-[¹⁸F]Fluoroethyl)-L-tyrosine ([¹⁸F]FET) PET is a valuable tool for the initial assessment of newly developed cerebral lesions, offering diagnostic and grading information for brain neoplasms. We aim to investigate clues for initial differential diagnosis in patients with newly developed cerebral lesions. We retrospectively analyzed 57 patients who underwent [¹⁸F]FET PET to evaluate newly diagnosed brain lesions. Tumor-to-brain ratios (TBRmax and TBRmean) of [¹⁸F]FET uptake were assessed to differentiate brain neoplastic lesions (BNLs) from non-neoplastic lesions (NNLs), and between tumor subgroups. [¹⁸F]FET uptake was significantly higher in BNLs compared to NNLs (TBRmax: 3.82 ± 1.41 vs 2.36 ± 0.60, P < 0.001; TBRmean: 2.22 ± 0.41 vs 1.70 ± 0.35, P < 0.001). ROC analysis identified a TBRmax cutoff of 2.77 to distinguish BNLs from NNLs (sensitivity: 86.7%, specificity: 78.6%, AUC: 0.837). Further analysis showed that high-grade tumors (e.g., high-grade gliomas and lymphoma) had higher TBRmax values than low-grade gliomas or NNLs (4.18 ± 1.31 vs 2.52 ± 1.09, P < 0.001), with a cutoff of 2.82 (sensitivity: 85.7%, specificity: 88.9%, AUC: 0.887, 95% CI: 0.779–0.996). [¹⁸F]FET PET uptake provides important diagnostic information for differentiating brain neoplasms from non-neoplastic lesions and helps stratify tumor grades at initial presentation.