ESTRO 2023 - Abstract Book

S432

Sunday 14 May 2023

ESTRO 2023

There is a negative correlation between the thickness of the cerebral cortex in the left temporal lobe and verbal memory at baseline. The radiation dose to the left cortex can potentially influence verbal memory at 1 year after treatment. In addition, there is a correlation between the changes in cortical thickness and verbal memory after treatment, which is influenced by age. MO-0551 Impact of pediatric irradiation on connectivity in learning and memory circuits (NCT04324450) E. Baudou 1 , P. Peran 1 , L. Pollidoro 1 , N. Courbieres 1 , G. Arribarat 1 , F. Tensaouti 2 , J. Tallet 1 , J. Danna 3 , J. Pariente 1 , Y. Chaix 1 , A. Laprie 1,4 1 Inserm, ToNIC, Toulouse neuroimaging center, Toulouse, France; 2 Institut Universitaire du Cancer de Toulouse-Oncopole, Radiation Oncology Department, Toulouse, France; 3 Aix Marseille Univ, CNRS, LNC, Marseille, France; 4 Institut Universitaire du Cancer de Toulouse-Oncopole, Radiation-Oncology department, Toulouse, France Purpose or Objective It is now well established that irradiation dose to the hippocampus has a negative impact on episodic memory and that a sparing approach led to a preservation of this neurocognitive function. Neuroimaging used to understand this impairment had focalized on structural parameters of the hippocampus. However, episodic memory is the result of complex connectivities between hippocampus and cortical brain areas. Moreover, other learning and memory processes are impaired in children after an irradiated posterior fossa tumor (PFT), especially working memory and procedural learning. The aim of this study was to explore the impact of a pediatric irradiation on long-term brain connectivity in circuits involved in learning and memories hypothesizing that irradiation of hippocampus has an impact on cortico-hippocampal circuit involved in episodic memory. In the same way, we hypothe that irradiation of cerebellum has an impact on cortico-cerebellar circuit involved in working memory and adaptative part of procedural learning; and irradiation of striatum has an impact on cortico-striatal connectivity involved in sequence learning part of procedural memory. Materials and Methods Twenty irradiated PFT survivors, fifteen non-irradiated and twenty-one healthy controls from the IMPALA study (NCT04324450) performed both a battery of memory tests assessing episodic, procedural and working memories, and a resting state functional MRI. Using a seed-based approach we built connectivity maps from 3DT1 manually contoured brain structures involved in memory (hippocampus, anterior and posterior cerebellum, caudate nucleus and putamen). Group comparisons were made and differences in connectivity were correlated with mnesic scores and mean irradiation dose received by the same brain structures reported from the initial dosimetry plans. Results Irradiated PFT had atypical connectivity in left cortico-hippocampal circuit, in right anterior cortico-cerebellar circuit, in left cortico-putamen circuit and in both cortico-caudate nucleus circuits compared to other groups. At behavioral level, all mnesic systems were impaired in irradiated PFT and relationships were found between cortico-hippocampal connectivity and episodic memory scores (especially learning a list of words r=0.58, p<0.01); and between cortico-striatal connectivity and sequence learning scores (r=0.62, p<0.01). Dosimetry data were available for seventeen irradiated PFT. Mean dose of irradiation to the caudate nucleus (r=-0.80, p<0.01), left putamen (r=-0.62, p=0.01) and left hippocampus (r=0.51, p=0.04) were linked with atypical connectivity in corresponding cortico-subcortical circuits. Conclusion This work highlights the long-term impact of irradiation on brain connectivity at rest in different brain circuits involved in learning and memory in pediatric PFT showing a specific dose-effect of irradiation for sus-tentorial structures. This is a step toward defining dose constraints to these structures in the future. MO-0552 Adult intracranial ependymoma - the role of DNA methylation in radiotherapeutic treatment decisions D. Kaul 1 , L. Schweizer 2 , E. Pérez 2 , S. Schmid 2 , C. Dittmayer 2 , K. Ichimura 3 , U. Schüller 4 , L. Dührsen 5 , M. Müther 6 , W. Paulus 7 , C. Thomas 7 , M. Gutt-Will 8 , P. Schucht 8 , T. Maragkou 9 , J. Schittenhelm 10 , F. Eckert 11 , M. Niyazi 12 , D. Fleischmann 13 , M. Dorostkar 14 , S. May 15 , J. Walter 16 , F. Ehret 1 , C. David 2 , M. Träger 1 1 Charité - Universitätsmedizin Berlin, Department of Radiation Oncology, Berlin, Germany; 2 Charité - Universitätsmedizin Berlin, Department of Neuropathology, Berlin, Germany; 3 National Cancer Center Research Institute, Division of Brain Tumor Translational Research, Tokyo, Japan; 4 University Medical Center Hamburg-Eppendorf, Institute of Neuropathology, Hamburg, Germany; 5 University Medical Center Hamburg-Eppendorf, Department of Neurosurgery, Hamburg, Germany; 6 University Hospital Münster, Department of Neurosurgery, Münster, Germany; 7 University Hospital Münster, Institute of Neuropathology, Münster, Germany; 8 Inselspital, Bern , Department of Neurosurgery, Bern, Switzerland; 9 University of Bern, Institute of Pathology, Bern, Switzerland; 10 University Hospital Tübingen, Institute of Pathology and Neuropathology, Tübingen, Germany; 11 University of Tübingen, Department of Radiation Oncology, Tübingen, Germany; 12 Ludwig-Maximilians-University Munich, Department of Radiation Oncology, Munich, Germany; 13 Ludwig-Maximilians-University Munich,, Department of Radiation Oncology, Munich, Germany; 14 Ludwig-Maximilians-University Munich, Center for Neuropathology, Munich, Germany; 15 Klinikum Chemnitz, Department of Neurosurgery, Chemnitz, Germany; 16 Jena University Hospital, Department of Neurosurgery, Jena, Germany Purpose or Objective A methylation-based classification of ependymoma has recently found broad application. However, the diagnostic advantage and implications for treatment decisions remain unclear. Here, we retrospectively evaluate the impact of surgery and radiotherapy on outcome after molecular reclassification of adult intracranial ependymomas. Materials and Methods Tumors diagnosed as intracranial ependymomas from 170 adult patients collected from eight diagnostic institutions were subjected to DNA methylation profiling. Molecular classes, patient characteristics, and treatment were retrospectively correlated with progression-free survival (PFS).