• Jens Gempt, Stefanie Bette, Niels Buchmann, Yu-Mi Ryang, Annette Förschler, Thomas Pyka, Hans-Jürgen Wester, Stefan Förster, Bernhard Meyer, and Florian Ringel.
• Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München, München, Germany. Electronic address: Jens.Gempt@tum.de.
• World Neurosurg. 2015 Dec 1; 84 (6): 1790-7.

BackgroundThe knowledge of exact tumor margins is of importance for the treating neurosurgeon, radiotherapist, and oncologist alike. The aim of this study was to investigate whether tumor volume and tumor margins acquired by magnetic resonance imaging (MRI) are congruent with the findings acquired by O-(2-(18F)-fluoroethyl)-L-tyrosine-positron emission tomography (FET-PET).MethodsPatients received FET-PET and MRI before surgery for brain metastases. Metastases were quantified by calculating tumor-to-background uptake ratios using FET uptake. PET and MRI-based tumor volumes, as well as areas of intersection, were assessed.ResultsForty-one patients were enrolled in the study. The maximum tumor-to-background uptake ratio measured in all of our patients harboring histologically proven viable tumor tissue was >1.6. Absolute tumor volumes acquired by FET-PET and MRI were not congruent in our patient cohort, and tumors identified in FET-PET and MRI only partially overlapped. The ratio of intersection (intersection of tumor defined by MRI and tumor defined by FET-PET at the ratio of tumor defined by FET-PET) was within a range of 0.27-0.68 when applying the different thresholds.ConclusionsOur study therefore indicates that treatment planning based on MRI or PET only might have a substantial risk of undertreatment at the tumor margins. These findings could have important implications for the planning of surgery as well as radiotherapy, although they have to be validated in further studies.Copyright © 2015 Elsevier Inc. All rights reserved.

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