ESTRO 2021 Abstract Book

S894

ESTRO 2021

Conclusion BMs patients pose a cognitively vulnerable population with limited survival. Nonetheless, this preliminary data indicates that performing a NCA and elaborate MRI pre- and three months post-RT is feasible and well- tolerated by the majority of patients. Moreover, the first MRI-derived parameters indicate that it is possible to identify subtle vascular changes both in the metastases and the rest of the brain pre-RT.

Digital Poster: Haematology

PO-1074 Is the mean heart dose the best predictor of cardiac toxicity after Hodgkin Lymphoma irradiation? R. Moujahed 1 , M. Ben Rejeb 1 , S. Ghorbel 1 , A. Hamdoun 1 , Z. Naimi 1 , M. Bohli 1 , L. Kochbati 1 1 Abderrahman Mami Hospital, Radiotherapy department, Ariana, Tunisia Purpose or Objective Radiationtherapy is an effective treatment for mediastinal Hodgkin lymphoma, but increases the risk of cardiovascular diseases, in long-term survivors, particularly ischemic events. The aim of our study was to evaluate the dose distribution to cardiac chambers and coronary arteries and to investigate the correlation between mean cardiac substructure doses and mean heart dose (MHD) as the only OAR dose constraint Materials and Methods We evaluated 25 patients with mediastinal hodgkin lymphoma treated with chemotherapy and involved-field radiation therapy (IFRT). The prescribed dose ranged from 19.8 to 36 Gy. Cardiac substructures including right ventricle (RV), left ventricle (LV), left atrium (LA), right atrium (RA), circumflex artery (CA), right coronary artery (RCA) and left anterior descending coronary artery (LAD) were delineated on CT Simulators, with 3mm thick slices, according to the cardiac countouring atlas of F. Duane. We calculated the MHD, the Dmean and the Dmax to cardiac substructures. A linear regression was performed individually for each cardiac substructure with mean heart dose as the independent variable. A coefficient of determination (r 2 ) was used to determine the presence or absence of a linear relationship. A coefficient of 0.7–1.0 was considered strong, 0.5–0.69 was moderate and 0.0–0.49 was weak. Results The mean and maximum heart dose were respectively 5.71 Gy and 14.29 Gy The most exposed structures were the LA (the mean Dmean and Dmax were respectively 10.1 and 26.69 Gy), the LAD (the mean Dmean and Dmax were respectively 6.87 and 21.91Gy) and the RA (the mean Dmean and Dmax were respectively 6.83 and 20.84 Gy). The mean Dmean and Dmax to the RCA were 9.18 Gy and 18.05 Gy. Both ventricles received the lowest doses. The RA (r 2 =0.85), the LA (r 2 =0.85) and the RV (r 2 =0.74) correlated strongly with mean heart dose. The RCA (r 2 =0.61) and the LAD (r 2 =0.57) had a moderate correlation with MHD Conclusion Among patients treated with mediastinal radiotherapy for Hodgkin lymphoma, both atriums and LAD are the most exposed cardiac substructures. The MHDwas found to be correlated strongly with mean cardiac cavities dose and moderately correlated with mean coronary arteries dose. The MHD may not be the best dosimetric parameter to predict late ischemic events risk. Further studies are needed to better define the dose-response relationship between cardiac disease and doses to specific cardiac substructures. PO-1075 Bridging Radiotherapy prior to Brexucabtagene Autoleucel CAR T-Cell Therapy in Mantle Cell Lymphoma N. Figura 1 , A. Sim 1 , S. Dahiya 2 , F. Lutfi 2 , A. Rapoport 2 , P. Mohindra 3 , A. Dohm 1 , J. Chavez 4 , B. Shah 4 , F. Khimani 5 , A. Lazaryan 5 , M. Davila 5 , C. Bachmeier 5 , T. Nishihori 5 , H. Liu 5 , S. Kim 1 , F. Locke 5 , M. Jain 5 , T. Robinson 1 1 H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, USA; 2 University of Maryland School of Medicine, Department of Medicine and Greenebaum Comprehensive Center, Baltimore, USA; 3 University of Maryland School of Medicine, Department of Radiation Oncology, Baltimore,