ESTRO 2023 - Abstract Book

S780

Monday 15 May 2023

ESTRO 2023

Conclusion The first developed detector showed satisfactory performance for applications in FLASH dosimetry, because the saturation and Cerenkov stem effect can be easily corrected. In addition, the prompt readout with a CCD camera provides immediate feedback and can readily be scaled to use for 1D and 2D arrays scintillating fibers, easily enabling 2D dosimetry. In the next developments, we will measure the percentage depth dose, the beam time and spatial profile in water, and we will also determine the dosimeters aging with irradiation.

Proffered Papers: Motion management

OC-0933 Automatically Triggered Surface-Based RT in DIBH in Breast Cancer - SAVE HEART dosimetry report S. Schönecker 1 , L. Angelini 2 , A. Gaasch 1 , M. Pazos 1 , M. Braun 3 , N. Harbeck 4 , M. Niyazi 1 , C. Belka 1 , S. Corradini 1 1 University Hospital LMU Munich, Department of Radiation Oncology, Munich, Germany; 2 University of Florence, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", Florence, Italy; 3 Red Cross Breast Centre, Department of Obstetrics and Gynecology, Munich, Germany; 4 University Hospital LMU Munich, Department of Obstetrics and Gynecology, Munich, Germany Purpose or Objective Adjuvant radiotherapy (RT) has an essential role in the management of early breast cancer (BC), where it increases local control, disease free survival and overall survival. On the other hand RT may lead to cardiovascular and lung toxicities. As known someRT strategies have been developed to optimize dosimetry, in particular for heart, left coronary artery (LAD) and lungs. Deep inspiration breath-hold (DIBH) favors the distancing of the heart from chest wall, minimizing the dose to intrathoracic organs without increasing low dose scatter or compromise target dose coverage. The aim of this prospective study, Save Heart, was to record and compare cardiac baseline risk and plan dosimetry to show the benefit of surface guided DIBH, using CatalystTM/SentinelTM system in left-sided BC patients. The study is registered in the German Register for Clinical Studies under the study number DRKS00011213. We report below on the dosimetric evaluations. Materials and Methods Inclusion criteria were a histologically confirmed left-sided invasive breast carcinoma or carcinoma in situ after breast conserving surgery (BCS) or mastectomy with indication for adjuvant radiotherapy of the residual breast/thoracic wall ± locoregional lymph drainage pathways, as well as the ability to hold breath for about 20 seconds. Treatments were hypofractionated (40.05 Gy in 15 fractions) or normofractionated (50.00 Gy in 25 fractions). From April 2014 to March 2021, 584 patients have been irradiated within the study. The deep inspiration irradiation was applied using the automatically triggered CatalystTM/SentinelTM system (C-RAD AB, Uppsala, Sweden) with audio- and video-feedback. CT and surface data were acquired both in DIBH and in free breathing (FB). Results Between all 584 patients, 363 were irradiated with hypofractionation (HF), while 221 with normofractionation (NF). All the results below show the dose reduction in DIBH vs FB plans. The mean heart dose was reduced by 35% in HF and by 36% in NF plans (respectively from 1.91 to 1.25 Gy and from 2.80 to 1.80 Gy, p<0.01). Heart Dmax was reduced by 42% in HF and by 40% in NF plans (respectively from 34.88 to 20.26 Gy and from 43.88 to 26.20 Gy, p<0.01). LAD D2cc was reduced by 55% in HF and by 56% in NF plans (respectively from 22.48 to 10.02 Gy and from 30.01 to 13.18 Gy, p<0.01). The mean lung dose was reduced by 12% in HF and by 14% in NF plans (respectively from 5.91 to 5.23 Gy and from 9.70 to 8.33 Gy, p<0.01). Conclusion To the best of our knowledge, this is the largest published prospective study showing a significant cardiac and lung protection from DIBH. In our opinion, all left-sided breast cancer patients with indication for radiation should be treated in deep inspiration if possible.