ESTRO 2022 - Abstract Book

S8

Abstract book

ESTRO 2022

time consuming and may take up to 4-6 weeks. Many patients in which CART therapy (CARTT) is indicated have symptomatic and progressive disease that requires some form of treatment to support them during the production period. Bridging therapy, referred to therapy administered after apheresis until CART infusion may be indicated. Selection of bridging treatment type is based on prior treatment, tumor load and symptoms. Early reports on radiotherapy as a bridging strategy have shown feasibility, safety and effectivity in this heavily pre-treated patient population. Patient numbers are limited and still little is known about the optimal dose, target definition and timing. Besides used as a bridging strategy, radiotherapy might play a role in optimizing CAR T-cell response, due to the immune modulating effect on both tumour cells and micro-environment.

Debate: Soft tissue sarcoma: Brachytherapy and/or EBRT or IORT - Current evidence

SP-0030 Value of EBRT

A. Levy 1 , C. Le Péchoux 1

1 Gustave Roussy, Radiation Oncology, Villejuif, France

Abstract Text Radiation therapy is a standard treatment for limbs soft tissue sarcomas. External-beam radiotherapy (EBRT) has been the most commonly used modality. Modern EBRT techniques such as conformal image-guided intensity modulated radiotherapy (IGRT/IMRT) could decrease the incidence of complications. Preoperative versus postoperative EBRT has been a controversial topic for years but the neoadjuvant schedule is henceforth gaining ground. Newer drug-EBRT combinations are also being prospectively assessed. EBRT must be personalized according to the histological subtype, the tumor site and the benefit/risk ratio, which is best appreciated by a multidisciplinary surgical and oncological team in a specialized center in the management of soft-tissue sarcomas.

SP-0031 Value of brachytherapy

M. Gimeno Morales

Spain Abstract not available

SP-0032 Value of IORT

F. Roeder 1

1 University of Salzburg, Radiation Oncology, Salzburg, Austria

Abstract Text In this talk, we will summarize the current evidence for IORT as a boost strategy preceeded or followed by EBRT in adult soft-tissue sarcomas of the extremity, trunk and retroperitoneal space and discuss the pros and cons of IORT in certain clinical situations. We will further present technical and practical considerations for state of the art performance of IORT based on the recently pupblished ESTRO-ACROP guideline for IORT in soft-tissue sarcoma, as well as further directions of IORT for example image-guided IORT.

Joint Symposium: ESTRO-EFOMP: CT innovations: DECT and beyond

SP-0034 Status and potential of dual-energy CT in radiotherapy

E. Baer 1

1 University College London, Medical Physics and Biomedical Engineering, London, United Kingdom

Abstract Text In recent years, the benefits of dual-energy computed tomography (DECT) for radiotherapy treatment planning were intensively investigated. In short, DECT imaging comprises the acquisition of two image sets of the same volume within the patient, each acquired with a different CT spectrum. These two image sets can be decomposed to achieve estimations of different radiological quantities. Physical and mathematical models can be applied to the acquired images or sinograms, resulting in maps of estimated electron/mass density, effective atomic number, relative stopping power (RSP), or elemental compositions. These maps have found the largest application in treatment planning and dose calculation of photon and particle therapy. Multiple research studies demonstrate that DECT-based estimates of electron/mass densities and RSP are superior to single- energy CT (SECT) estimates of the same quantity. For example, experimental studies investigating the accuracy of predicted RSP values for proton therapy in porcine and bovine tissues consistently report RSP predictions better than 1% accuracy using DECT as compared to over 2% using SECT. To take this a step further, it was demonstrated by multiple research groups independently that this improved RSP prediction leads to decreased beam range uncertainty.