title: 18F-FET PET Uptake Characteristics in Patients with Newly Diagnosed and Untreated Brain Metastasis.
abstract: In patients with brain metastasis, PET using labeled amino acids has gained clinical importance, mainly regarding the differentiation of viable tumor tissue from treatment-related effects. However, there is still limited knowledge concerning the uptake characteristics in patients with newly diagnosed and untreated brain metastases. Hence, we evaluated the uptake characteristics in these patients using dynamicO-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) PET.Methods:Patients with newly diagnosed brain metastases without prior local therapy and18F-FET PET scanning were retrospectively identified in 2 centers. Static and dynamic PET parameters (maximal/mean tumor-to-brain-ratio [TBRmax/TBRmean], biologic tumor volume [BTV], and time-activity curves with minimal time to peak [TTPmin]) were evaluated and correlated with MRI parameters (maximal lesion diameter, volume of contrast enhancement) and originating primary tumor.Results:Forty-five brain metastases in 30 patients were included. Forty of 45 metastases (89%) had a TBRmax≥ 1.6 and were classified as18F-FET-positive (median TBRmax, 2.53 [range, 1.64-9.47]; TBRmean, 1.86 [range, 1.63-5.48]; and BTV, 3.59 mL [range, 0.04-23.98 mL], respectively). In 39 of 45 brain metastases eligible for dynamic analysis, a wide range of TTPminwas observed (median, 22.5 min; range, 4.5-47.5 min). All18F-FET-negative metastases had a diameter of ≤ 1.0 cm, whereas metastases with a > 1.0 cm diameter all showed pathologic18F-FET uptake, which did not correlate with lesion size. The highest variability of uptake intensity was observed within the group of melanoma metastases.Conclusion:Untreated metastases predominantly show increased18F-FET uptake, and only a third of metastases < 1.0 cm were18F-FET-negative, most likely because of scanner resolution and partial-volume effects. In metastases > 1.0 cm,18F-FET uptake intensity was highly variable and independent of tumor size (even intraindividually).18F-FET PET might provide additional information beyond the tumor extent by reflecting molecular features of a metastasis and might be a useful tool for future clinical applications, for example, response assessment.
authors.affiliation: Department of Nuclear Medicine, University of Munich (LMU), Munich, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Unterrainer
authors.affiliation: Institute of Neuroscience and Medicine, Research Center Juelich, Juelich, Germany.|Department of Neurology, University Hospital Cologne, Cologne, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Galldiks
authors.affiliation: Department of Neurosurgery, LMU, Munich, Germany.
authors.forename: Bogdana
authors.initials: B
authors.lastname: Suchorska
authors.affiliation: Department of Nuclear Medicine, University of Munich (LMU), Munich, Germany.
authors.forename: Lara-Caroline
authors.initials: LC
authors.lastname: Kowalew
authors.affiliation: Department of Nuclear Medicine, University of Munich (LMU), Munich, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Wenter
authors.affiliation: Institute for Clinical Radiology, LMU, Munich, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Schmid-Tannwald
authors.affiliation: Department of Radiation Oncology, LMU, Munich, Germany.|German Cancer Consortium (DKTK) & German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Niyazi
authors.affiliation: Department of Nuclear Medicine, University of Munich (LMU), Munich, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bartenstein
authors.affiliation: Institute of Neuroscience and Medicine, Research Center Juelich, Juelich, Germany.|Department of Nuclear Medicine, University of Aachen, Aachen, Germany; and.|JARA-Brain Section, Juelich-Aachen-Research-Alliance (JARA), Juelich, Germany.
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Langen
authors.affiliation: Department of Nuclear Medicine, University of Munich (LMU), Munich, Germany nathalie.albert@med.uni-muenchen.de.
authors.forename: Nathalie L
authors.initials: NL
authors.lastname: Albert
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D001692:Biological Transport; D001812:Blood-Brain Barrier / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000378:metabolism / Q000556:secondary*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; C545932:(18F)fluoroethyltyrosine; D014443:Tyrosine
keywords: 18F-FET PET; brain metastasis; kinetic analysis