• Markus Hutterer, Martha Nowosielski, Daniel Putzer, Nathalie L Jansen, Marcel Seiz, Michael Schocke, Mark McCoy, Georg Göbel, Christian la Fougère, Irene J Virgolini, Eugen Trinka, Andreas H Jacobs, and Günther Stockhammer.
• Department of Neurology, Wilhelm-Sander Neurooncology Therapy Unit, University Hospital of Regensburg, Universitätsstrasse 84, D-93053 Regensburg, Germany. markus.hutterer@kabelmail.de
• Neuro-oncology. 2013 Mar 1; 15 (3): 341-51.

BackgroundTo assess the sensitivity and specificity of [(18)F]-fluoro-ethyl-l-tyrosine ((18)F-FET) PET in brain tumors and various non-neoplastic neurologic diseases.MethodsWe retrospectively evaluated (18)F-FET PET scans from 393 patients grouped into 6 disease categories according to histology (n = 299) or distinct MRI findings (n = 94) (low-grade/high-grade glial/nonglial brain tumors, inflammatory lesions, and other lesions). (18)F-FET PET was visually assessed as positive or negative. Maximum lesion-to-brain ratios (LBRs) were calculated and compared with MRI contrast enhancement (CE), which was graded visually on a 3-point scale (no/moderate/intense).ResultsSensitivity and specificity for the detection of brain tumor were 87% and 68%, respectively. Significant differences in LBRs were detected between high-grade brain tumors (LBR, 2.04 ± 0.72) and low-grade brain tumors (LBR, 1.52 ± 0.70; P < .001), as well as among inflammatory (LBR, 1.66 ± 0.33; P = .056) and other brain lesions (LBR, 1.10 ± 0.37; P < .001). Gliomas (n = 236) showed (18)F-FET uptake in 80% of World Health Organization (WHO) grade I, 79% of grade II, 92% of grade III, and 100% of grade IV tumors. Low-grade oligodendrogliomas, WHO grade II, had significantly higher (18)F-FET uptakes than astrocytomas grades II and III (P = .018 and P = .015, respectively). (18)F-FET uptake showed a strong association with CE on MRI (P < .001) and was also positive in 52% of 157 nonglial brain tumors and nonneoplastic brain lesions.Conclusions(18)F-FET PET has a high sensitivity for the detection of high-grade brain tumors. Its specificity, however, is limited by passive tracer influx through a disrupted blood-brain barrier and (18)F-FET uptake in nonneoplastic brain lesions. Gliomas show specific tracer uptake in the absence of CE on MRI, which most likely reflects biologically active tumor.

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