ESTRO 2024 - Abstract Book

S6027

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

3090

Poster Discussion

Motor-fiber tractography in neoadjuvant stereotactic radiotherapy of brain metastases

Carolina Bernauer 1,2 , Sarah Stefanowicz 1 , Enrike Rosenkranz 3 , Maximilian J Schwendner 2,4 , Mathias Düsberg 1 , Juliana Martins 1 , Martin Misslbeck 1 , Nico Sollmann 5 , Malin L Tröndle 1,2 , Maximilian Aigner 1 , Maria Waltenberger 1 , Sebastian Ille 2,4 , Arthur Wagner 2 , Bernhard Meyer 2 , Stephanie E Combs 1 , Sandro M Krieg 2,4 , Christian D Diehl 1 1 School of Medicine, Klinikum rechts der Isar, Department of Radiation Oncology, Munich, Germany. 2 School of Medicine, Klinikum rechts der Isar, Department of Neurosurgery, Munich, Germany. 3 School of Medicine, Klinikum rechts der Isar, Department of Diagnostic and Interventional Neuroradiology, Munich, Germany. 4 University Hospital Heidelberg, Department of Neurosurgery, Heidelberg, Germany. 5 University Hospital Ulm, Department of Diagnostic and Interventional Neuroradiology, Ulm, Germany Symptomatic and large brain metastases should be resected according to current guidelines. In particular, especially lesions close to motor cortex and corticospinal tract (CST) likely cause motor deficits, hence requiring neurosurgical removal. To date, adjuvant stereotactic radiotherapy of the resection cavity is standard of care to significantly reduce the high risk of local recurrence. However, target volume definition can be challenging due to the irregular configuration and size dynamics of the resection cavity. For this reason, neo-adjuvant stereotactic radiotherapy (N RT) of metastases offers the advantage of easy target volume definition as well as reduced dose exposure to surrounding brain tissue due to smaller safety margins and omission of the surgical tract. In neurosurgery, navigated transcranial magnetic stimulated (nTMS) motor cortex maps as well as associated DTI-based fiber tracts are intraoperatively respected for resection of eloquent brain metastases. In contrast, however, primary motor structures are not standardly considered in RT planning so far. This work investigates the application of nTMS/DTI based motor areas in N-RT. 9 patients harbouring symptomatic brain metastases close to the primary motor areas that had undergone resection were analysed. Reconstructions of the individual motor cortex and CST were preoperatively derived by combining nTMS motor mapping and DTI tractography. FTmot.TMS were retrospectively incorporated into the RT planning system and merged with the planning imaging originally used for adjuvant hFSRT. Then, tracts were delineated as partial risk volume (PRV.FTTMS) and defined as OAR. Metastases were contoured as gross target volume (GTV) with 1mm expansion for the planning target volume (PTV). For each patient hypo-fractionated stereotactic radiotherapy (hFSRT) 7 x 5 Gy plans were calculated: 1. Leksell Gamma Knife® (LGK, Elekta, Sweden) plans with dose prescription to the enclosing 70% isodose and 2. volumetric intensity modulated arc (VMAT) plans with dose prescription to the enclosing 80% isodose. Dose exposition of PRV-FTTMS and dose-volume histogram parameters were compared for LGK and VMAT. Mean values ±SD are given if not otherwise indicated. Level of significance was set at p < 0.05. Purpose/Objective: Material/Methods:

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