ESTRO 2023 - Abstract Book

S1813

Digital Posters

ESTRO 2023

Fig2: Plan evaluation parameters.

Conclusion The use of the ASC tool did not significantly impact metrics, dose restrictions or quality controls. Nevertheless, there was a significant reduction in the number of Mus that should be highlighted. The combination ML+ASC showed significant changes in 60% of the items evaluated. The overall quality of treatments showed an improvement through progress in the conformity index and, consequently, a decrease in MUs.

PO-2041 Heart-sparing techniques and heart dose constrains used in clinical practice in Europe

F. Kraja 1 , M. Chiril ă 2,2 , P. Franco 3 , P. Poortmans 4 , I. Ratosa 5

1 University Hospital Center Mother Teresa, Oncology, Tirana, Albania; 2 MVision AI, AI Innovation for Radiotherapy, Helsinki, Finland; 3 University of Eastern Piedmont, Department of Translational Sciences (DIMET), Novara, Italy; 4 University of Antwerp, Faculty of Medicine and Health Sciences, Department of Radiation Oncology, Iridium Netwerk, Wilrijk-Antwerp, Belgium; 5 Medical Faculty, University of Ljubljana, Division of Radiation Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia Purpose or Objective Adverse cardiac events in patients who have received radiation therapy (RT) for breast cancer (BC) treatment are associated to the heart dose received, for example Dmean and various DVH-parameters of both the heart and cardiac substructures. We aimed to asses the variation of heart dose constrains and heart-sparing techniques used in the clinical practice in Europe. Materials and Methods An online survey was disseminated amongst radiation oncologists (ROs) in Europe through personal, RO and BC societies’ networks, from October 2019 to March 2020. Demographics, clinical practice and dosimetry constraints used in BC RT clinical practice were analysed. Descriptive statistical analyses and chi-squared testing were done using SPSS version 26 (SPSS, Chicago, IL). Results A total of 412 from 44 countries responded to the questionnaire. As heart-sparing techniques, IMRT and VMAT were the most commonly employed approaches, with 54.1% and 51.7%, respectively; deep inspiration breath hold (DIBH) was used by 43.2%, partial breast irradiation (PBI) by 32.8%, prone position by 16.8% of the respondents and protons by 4.3%. There was no difference in the use of PBI in academic vs non-academic institutions (53.7% vs 46.3%). The use of PBI was higher in Western vs Eastern Europe (59.4% vs 40.6%). DIBH was mostly used in the following clinical scenarios: for all patients with left-sided BC (37.2%), only selected patients with left-sided BC (32.6%), patients with right-sided BC (21.8%) or for patients with billateral BC (26.5%). About 26.5% ROs reported not using DIBH at all. The main reasons for choosing DIBH were lung and heart sparing (45.1% and 41.3%, respectively), coronary arteries avoidance (33.0%) and liver sparing (17.5%). Details on organs-at-risk (OAR) dose constraints used for treatment planning process were provided by a variable number of respondents (3.2–35.6%) and reported percentages are calculated upon their answers. The most commonly used dose constraint for OAR in clinical practice was Heart Dmean. The median Heart Dmean threshold, reported by 35.6% ROs, to be used in clinical practice, was 4 Gy (1–30). Even fewer (3.2–7.7%) ROs reported using dose-volume parameters, such as V10– 40 Gy. Of 140 ROs reporting Heart Dmean, less than one third (27.9%) applied stringent constraints for Heart Dmean of less than 3.0 Gy. Dose-volume parameters for cardiac substructures were also rarely reported, with only 8.7% of responding ROs using left coronary artery dose constraints and 3.2% of ROs reported using left ventricular dose constraints. The Heart Dmean was statistically significantly correlated with the use of ESTRO 2015 breast contouring guideline (p=0.038), use of hypofractionation (p=0.029), DIBH (p=0.001) and PBI (p=0.001), but not with the use of RTOG guidelines (p=0.308). Conclusion In Europe, technology for heart sparing techniques, and OAR dose constraints vary greatly. Clinical practice needs consensus on OAR dose constraints for various indications.

PO-2042 Plan quality & deliverability of IMRT plans for lung cancer using various leaf motion calculators