18F-FET-PET hypermetabolic brain lesions: A correlation study to MRI and histopathologic findings.

Abstract

2042 Background: Due to the specific incorporation of 18F-fluoroethyl-L-tyrosine (18F-FET) into glioma cells, a number of studies have proven the clinical value of 18F-FET-PET to identify brain lesions as gliomas and to determine the extent of the brain tumor for treatment planning and biopsy guidance. However, the specificity of 18F-FET-PET in brain tumor diagnosis is still unknown. Therefore, the aim of this study was to correlate 18F-FET-PET hypermetabolic brain lesions to histopathologic diagnosis and MRI findings. Methods: We retrospectively analysed pre- and post-operative 18F-FET-PET scans of 200 patients with suspected neoplastic brain lesions and compared the results to MRI and histopathologic findings. Results: Comparison of preoperative 18F-FET-PET metabolic active brain lesions with histopathologic findings revealed that not only glial tumors, but also other primary brain tumors, including anaplastic ependymoma, primitive neuroectodermal tumors, medulloblastoma, primary CNS lymphoma, pinealoblastoma, acoustic neuroma, anaplastic meningeoma, inflammatory multiple sclerosis and ADEM lesions were 18F-FET hypermetabolic. 18F-FET activity in inflammatory lesions was remarkably lower than in tumor lesions. In some cases after macroscopic total resection of a malignant glioma and no residual tumor on MRI, 18F-FET-PET clearly identified residual tumor burden. FET-PET was helpful to discriminate between post-radiation necrosis/pseudoprogression and tumor recurrence. Conclusions: 18F-FET-PET hypermetabolism is detectable in various neoplastic and inflammatory brain lesions limiting the specificity for glial tumors. After histopathologic diagnosis of a glial tumor 18F-FET-PET scans are sensitive to identify residual tumor after neurosurgical intervention, which should be implemented in radiotherapy planning. Pre- and postoperative 18F-FET-PET scans may also be helpful to guide stereotactic biopsy or surgery and to discriminate necrosis/pseudoprogression from tumor recurrence. No significant financial relationships to disclose.