ESTRO 2020 Abstract book

S426 ESTRO 2020

The robotic device was able to tap the needle into the prostate to the planned needle depths of 105 and 104 mm with respect to the perineum surface for patient 1 and 2, respectively. The robotic needle insertion and dose delivery (including setup, anesthesia, catheter insertion, MR scanning, reconstruction and planning) took 2 hours, of which the needle insertion itself took 10 minutes. ∆x, ∆y, ∆z deviations between the realized needle tip position and the planned position were 7.1, 5.5, -3.4 mm and 0.5, 3.0, 1.1 mm for patient 1 and 2, respectively (see figure 1). The translation and rotation of the prostate between the prescan and the postscan amounted 1.5, -1.1, 0.9 mm and -1.0 o , 0.5 o , 1.5 o for patient 1 and -0.2, -0.1, -0.7 mm and -0.3 o , 0.0 o , 0.0 o for patient 2. There was no indication of bending of the needle in both patients. Conclusion This first in vivo test shows that MRI guided robotic needle insertion is feasible with increasing accuracy to <3 mm and limited prostate movement in the order of 1 mm.

dosimetric data and results of the neuropsychological assessments performed in high-grade glioma (HGG) patients. A new concept of dose constraints would be introduced for intensity-modulated radiotherapy in brain tumours. Material and Methods A bicentric study has been recruiting 174 patients treated with concurrent chemoradiotherapy for supratentorial HGG since 2015 (ClinicalTrials.gov identifier: NCT02544178). Focal brain radiotherapy was performed following surgical biopsy or excision. Temozolomide was administered daily concurrently with radiotherapy. Delineation of the brain areas implied in cognitive functions, e.g. both hippocampi, subventricular zones, the corpus callosum, the frontal and temporal lobes, the normal brain, i.e. the brain minus the Planning Target Volume (PTV), was performed for each patient using computed tomography and magnetic resonance imaging. Dose prescription was 60 Gy in 30 daily fractions to the PTV. Neuropsychological assessments were performed at baseline, i.e. after surgery and before chemoradiotherapy, then annually by specialised teams. Logistic functional regression was used to define the dosimetric parameters associated with the risk of cognitive decline at one year following the completion of chemoradiotherapy. Statistical significance was reached when p-level was below 0.05. Results A cohort of 40 surviving patients having performed the neuropsychological assessment at one year was considered for analyses. Median PTV was 240 cc (89-440). The main PTV locations were the right frontal lobe (27.5%) and the right temporal lobe (22.5%). At least one cognitive function was altered in 34 patients (85%) at baseline and at one year. Median doses to both hippocampi, the left subventricular zone and the left frontal lobe were associated with a significant risk of impairment of the general cognitive assessment, the verbal episodic memory and the processing speed at one year (p<0.05 in the three cases). Median doses of 20 Gy and 25 Gy to the normal brain exposed to a risk of 20% and 40% of alteration of the general cognitive assessment, respectively (p=0.009). Maximal respective doses of 42 Gy and 53 Gy to the left temporal lobe were correlated with probabilities of 10% and 20% of the verbal episodic memory decline (p=0.014). In multivariate analysis, a PTV upper than 320 cc exposed to a significant risk of alteration of the general cognitive assessment at one year (p=0.048). Conclusion This prospective study finds statistically significant correlations observed between dose distributions to various brain areas and late cognitive impairment. These results have to be confirmed in a higher number of patients in order to validate new relevant dose constraints to the healthy tissues implied in cognitive functions.

OC-0696 Development of dose constraints to the brain areas implied in cognition: a prospective study J. Jacob 1 , M. Ribeiro 2 , M.A. Benadjaoud 3 , C. Jenny 4 , L. Feuvret 1 , J. Simon 1 , M. Bernier 5 , D. Antoni 6 , K. Hoang- Xuan 2 , D. Psimaras 2 , A. Carpentier 7 , D. Ricard 8 , P. Maingon 1 1 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Radiation Oncology, Paris, France ; 2 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Neurology 2, Paris, France ; 3 institut De Radioprotection Et De Sûreté Nucléaire, Radiobiology And Regenerative Medicine Research Service- Direction Of Human Health, Fontenay-Aux-Roses, France ; 4 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Medical Physics, Paris, France ; 5 institut De Radioprotection Et De Sûreté Nucléaire, Laboratory Of Epidemiology, Fontenay-Aux-Roses, France ; 6 centre Paul Strauss, Department Of Radiotherapy, Strasbourg, France ; 7 groupe Hospitalier Pitié-Salpêtrière-Charles Foix, Department Of Neurosurgery, Paris, France ; 8 hôpital D'instruction Des Armées Percy, Department Of Neurology, Clamart, France Purpose or Objective This prospective work aims at elaborating dose constraints to the brain areas implied in cognitive functions using the

Proffered Papers: Proffered papers 36 - Managing uncertainties in proton therapy

OC-0697 Particle therapy: Assessing clinical benefit of direct stopping-power prediction from dual-energy CT N. Peters 1,2 , P. Wohlfahrt 1,2,3 , C. Hofmann 4 , C. Möhler 4 , S. Makocki 5 , C. Richter 1,2,5,6 1 OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden- Helmholtz-Zentrum Dresden - Rossendorf, Dresden,