ESTRO 2023 - Abstract Book

S2118

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ESTRO 2023

Only 6 patients had received a concurrent chemotherapy . The median dose of RT was 52.2 Gy (52.2-66y). The target volumes were the tumor bed and cervical lymph nodes bothesides including in most cases level II,III,IV and VI .The median Dmean to the carotid arteries was 48Gy(40-59Gy).The median Dmax was 58Gy (56-77Gy) .The median Dmin was 20Gy(12- 40Gy) .After a median follow-up of 48 months(12– 96) ,most patients were in a complete remission (80%).Only 4 patients (10%) has experienced an ICVE .Of these events, 1 was left-sided and 3 were right-sided .The median time to ICVE was 24 months .We noted that none of the patients had a Doppler ultrasound follow-up of the vascular axes since the end of RT.The impact of patient characteristics was observed, although a trend was seen for risk factors for cardiovascular events such as smoking ,hypertention ,atherosclerosis and family history of cardiovascular diseases (p < 0.02). Conclusion PORT for laryngeal cancer can lead to an unavoidable strokes , because of the inevitable high dose received by the CA wich is mostly included in the radiation field .The data in the literature are still insufficient to predict the dose-effect correlation at the CA , and the risk of occurrence of ICVE in those patients. Thus, the optimization of the RT technique and the establishment of strict long-term monitoring of those patients are required especially for those with a personal or family history of vascular disease. 1 Humanitas Research Hospital, Humanitas University, Radiotherapy, Rozzano, Milano, Italy; 2 Humanitas University, Department of Biomedical Sciences, Rozzano, Milano, Italy; 3 Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, Milano, Italy; 4 IRCCS Humanitas Research Hospital, Humanitas University, Radiotherapy, Rozzano, Milano, Italy; 5 IRCCS Humanitas Research Hospital, Medical Physics Unit, Rozzano, Milano, Italy Purpose or Objective Total marrow/lymph node irradiation (TMI/TMLI) is a modulated radiotherapy technique for delivering full dose to the hematological target and sparing the dose from organs at risk (OARs) within the conditioning regimen before bone marrow transplantation. The TMI/TMLI target includes the whole bones, lymph-node system, and spleen. In particular, the lymph- node chains delineation is the most demanding contouring. We evaluated the impact of introducing internal contouring guidelines to reduce the inter- and intra-variability of lymph-node contour in TMI/TMLI. Materials and Methods Since 2010, 114 patients were treated in our center with TMLI using volumetric modulated arc therapy (VMAT). Ten patients were randomly selected from the internal database. The lymph-nodes clinical target volume (CTV_LN) was re-contoured according to new internal guidelines (GL) by a single expert radiation oncologist (CTV_LN_GL_RO1), and compared to the historical one (CTV_LN_Old). The guidelines efficacy in reducing inter- and intra-variability was prospectively evaluated in, respectively, six and four patients. The CTV_LN was splitted in four regions (H&N, Thoracic, Abdominal, and Pelvic areas) for better evaluate the agreement. Dice similarity coefficient (DSC) was calculated for all paired contours. Planning target volume (PTV_LN) was generated adding an isotropic margin of 5 mm to the CTV_LN. The TMI/TMLI plans were optimized on PTV_Tot (=PTV_bones+PTV_LN+PTV_spleen) using PTV_LN_old for retrospective patients and PTV_LN_RO1 for prospective patients. The volume received by the 95% of the prescription dose (V95%) were computed for all contours to assess the target coverage and guidelines consistency. Results A total of 250 target volumes were considered. Median CTV_LN and PTV_tot were, respectively, 2100±610 cm3 and 16221±2587 cm3. The mean DSCs were 0.82±0.09, 0.97±0.01, and 0.98±0.02 for, respectively, CTV_LN_Old vs. PO-2355 Internal guidelines to reduce lymph-node contour variability for total marrow/lymph node irradiation D. Dei 1 , N. Lambri 2 , L. Crespi 3 , R. Coimbra Brosio 3 , D. Loiacono 3 , M. Scorsetti 4 , P. Mancosu 5