ESTRO 2023 - Abstract Book

S1173

Digital Posters

ESTRO 2023

Conclusion More patients with relative citrulline levels ≤ median experienced late bowel toxicity and late diarrhoea than those with relative citrulline levels > median. The percentage difference in patients with 1 MCIC for late diarrhoea stratified by relative citrulline levels was greater than by treatment group. Citrulline has potential as a predictive biomarker of late bowel toxicity, particularly diarrhoea, in patients treated with prostate radiotherapy. Findings are limited by low study numbers, however, if supported by further research, citrulline levels would allow for adjustment of radiotherapy to reduce the risk of late toxicity in selected patients.

PO-1448 Perfusion MRI and MRI spectroscopy: biomarkers of memory decline in pediatric brain tumor survivors

F. TensaoutI 1,2 , N. Courbières 2 , A. Troudi 2 , E. Baudou 2,3 , L. Pollidoro 2 , P. Péran 2 , G. Arribarat 2 , J. Tallet 2 , J. Danna 4 , J. Pariente 2,5 , Y. Chaix 2,6 , A. Laprie 7,8 1 Institut Claudius Regaud- Institut Universitaire du Cancer de Toulouse-Oncopole, Radiation Oncology , Toulouse, France; 2 Toulouse NeuroImaging Center (ToNIC), INSERM-University of Toulouse Paul Sabatier, Research, Toulouse, France; 3 Children's Hospital, Toulouse University Hospital, Pediatric Neurology , Toulouse, France; 4 Aix Marseille Univ, CNRS, LNC, Research, Marseille, France; 5 Toulouse University Hospital, Neurology Department, , Toulouse, France; 6 Children's Hospital, Toulouse University Hospital, Pediatric Neurology Department, Toulouse, France; 7 Toulouse NeuroImaging Center (ToNIC), INSERM-University of Toulouse Paul Sabatier, Research, Toulouse, France; 8 Institut Claudius Regaud- Institut Universitaire du Cancer de Toulouse-Oncopole , Radiation Oncology, Toulouse, France Purpose or Objective Posterior fossa tumors (PFT) represent two thirds of brain tumors in children. Although progress in treatment has improved survival rates over the past few years, long-term impairments in memory are frequent. The hippocampi, cerebellum and striatum play a role respectively in episodic and semantic, working and procedural memory. They are affected not only by the location of the tumor itself and the surgery, but also by the complementary treatments, particularly radiotherapy (RT). The aim of this work was to investigate new MRI biomarkers of cognition decline using perfusion MRI with arterial spin labelling (ASL) and 3D MRI spectroscopy (MRSI). Materials and Methods Sixty participants, divided into 3 groups, were included in this prospective IMPALA study (NCT04324450): the first 2 groups included patients considered to be cured and completed treatment at least 5 years earlier, either with RT (G1: 22 patients) or without RT (G2: 17 patients), G3 included healthy subjects matched with G1 for age, sex, and handedness. All participants performed neuropsychological tests, including an assessment of the main memory systems and undergo multimodal MRI (Philips Achieva dStream 3.0 T). After image post-processing, metabolite values (choline (Cho), N acetylaspartate (NAA), creatine (Cr)) were extracted in cerebellum and mean perfusion values were extracted from ASL perfusion weighted maps. Mean and maximum doses at hippocampus, caudate nucleus, putamen, thalamus and cerebellum were collected from the initial dosimetry plan. The comparisons between groups were made with the Chi-square, Fisher's exact, or Kruskal Wallis tests. Correlations were evaluated using Spearman's rank coefficient. Results Median values of Cho, Cr, NAA and ratio of NAA to the sum of metabolites were significantly lower in G1 &G2 compared to healthy subjects (P<0.05). Scores of working and procedural memories tests were significantly lower in G1& G2 (P<0.004) and correlated to median and maximum values of Cho and NAA (0.28< r <0.49, p<0.04). For others brain structures, statistically significant differences in perfusion values were found between G1 & G3 (P<0.05).