ESTRO 2020 Abstract book

S894 ESTRO 2020

PO-1558 Model based target definition for high-grade gliomas: implementation and sensitivity analysis W. Häger 1 , M. Lazzeroni 1 , M. Astaraki 2,3 , I. Toma-Dasu 1,3 1 Stockholm University, Department of Physics, Stockholm, Sweden ; 2 Royal Institute of Technology, Department of Biomedical Engineering and Health Systems, Huddinge, Sweden ; 3 Karolinska Institute, Department of Oncology and Pathology, Stockholm, Sweden Purpose or Objective High-grade gliomas are known to infiltrate normal tissue (NT). This invasion is accounted for in radiotherapy by applying margins, potentially resulting in a large volume of the brain to be irradiated. This limits the deliverable dose and prognosis is extremely poor. A radiotherapy option could be stereotactic radiosurgery (SRS) using the Leksell Gamma Knife®, which can produce highly conformal dose distributions to the target with steep dose gradients at the border. However, its applicability to treating high-grade gliomas is limited by the inability to predict the target extension. The aim of this study was to implement a model for predicting the NT invasion by glioma cells to be used for accurate target delineation for SRS and to perform a sensitivity analysis of the model predictions with respect to its parameters. Material and Methods The infiltrative character of gliomas was described by a function of tumour cell density on the distance from the visible border of the tumour volume. The function used was given by the Fisher-Kolmogorov model for tumour spread. The model employs a partial differential equation with respect to time and accounts for cell diffusion (D) and cell proliferation (ρ). The diffusion coefficient assumes different values for white and grey matters (D W , D G ) and is zero everywhere else. An important parameter is the ratio D/ρ which determines the gradient of the tumour cell density function. There is no consensus in the literature on the values of D/ρ and D W /D G . The model for the tumour spread was implemented on a contrast enhanced T1 MRI brain scan. The image was segmented with respect to the diffusion coefficients. The model was solved in MATLAB using a finite-domain time-difference method. The values of D/ρ used ranged between 0.25 mm 2 and 25 mm 2 and the values of D W /D G were 5, 10, and 100, as found in the literature. The simulations were run until the volume encompassed by the tumour cell density visibility threshold isoline was reached (8000 cells/mm 3 ). The volumes encompassed by the isoline with 1000 cells/mm 3 (V 1000 ) were investigated as a function of D/ρ and D W /D G . Results Figure 1a shows isolines/contours of simulated tumours for various values of D/ρ and D W /D G = 10. Despite having roughly the same detectable volumes (encompassed by the red isoline), the actual tumour extension (the green and blue isolines) increases with increasing D/ρ. Figure 1b shows V 1000 (normalized) plotted as a function of D/ρ and D W /D G . There is a clear trend of an increase in tumour volume with an increase in D/ρ. The tumour invasiveness does not appear to be dependent on D W /D G .

Conclusion Mathematical modelling of the invasiveness and tumour extension of high-grade gliomas could be used for guiding the delineation of stereotactic radiosurgery targets with invasive character. The actual invasiveness and extension of the tumour depend on the cell diffusion and cell proliferation ratio, D/ρ, but do not appear to be influenced by D W /D G . PO-1559 Survival prediction in GBM using radiomics of multimodal imaging F. Tensaouti 1,2 , J. Bailleul 1,2 , E. Martin 3 , F. Desmoulin 2 , S. Ken 4 , J. Desrousseaux 1 , L. Vieillevigne 4 , J. Lotterie 2,5 , V. Lubrano 6 , I. Catalaa 7 , G. Noël 8 , G. Truc 9 , M. Sunyach 10 , M. Charissoux 11 , N. Magné 12 , T. Filleron 3 , P. Péran 2 , E. Cohen-Jonathan Moyal 1,13 , A. Laprie 1,2 1 Institut Claudius Regaud/Institut Universitaire du Cancer de Toulouse – Oncopôle, Radiation oncology, Toulouse, France ; 2 ToNIC- Toulouse NeuroImaging Center- Université de Toulouse- Inserm- UPS- Inserm 1214, Research, Toulouse, France ; 3 Institut Claudius Regaud/Institut Universitaire du Cancer de Toulouse – Oncopôle, Biostatistics, Toulouse, France ; 4 Institut Claudius Regaud/Institut Universitaire du Cancer de Toulouse – Oncopôle, Engineering and Medical Physics, Toulouse, France ; 5 CHU Toulouse, Nuclear Medicine, Toulouse, France ; 6 CHU Toulouse, Neurosurgery, Toulouse, France ; 7 CHU Toulouse, Radiology, Toulouse, France ; 8 Centre Paul Strauss, Radiation oncology, Strasbourg, France ; 9 Centre Georges-François Leclerc, Radiation Oncology, Dijon, France ; 10 Centre Léon- Bérard, Radiation oncology, Lyon, France ; 11 Institut du Cancer de Montpellier, Radiation Oncology, Montpellier, France ; 12 Institut de Cancérologie de la Loire Lucien Neuwirth, Radiation oncology, Saint-Priest-en-Jarez, France ; 13 Inserm U1037- Centre de Recherches contre le Cancer de Toulouse, Research, Toulouse, France

Purpose or Objective Background

Gliomics is a research project with the goal of extracting radiomics from multimodal imaging data of multicenter SPECTRO GLIO prospective phase III trial for newly diagnosed glioblastoma (NCT01507506) [1]. The aim of this