ESTRO 2021 Abstract Book

S949

ESTRO 2021

1 Université Catholique de Louvain, 1. Institut de Recherche Experimentale et Clinique (IREC), Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Brussels, Belgium; 2 Cliniques Universitaires Saint-Luc, Radiation Oncology, Brussels, Belgium Purpose or Objective By minimizing radiation-induced cardiac and lung toxicity for left breast cancer, gated irradiation during deep inspiration breath-hold (DIBH) has become a standard of care. Refinements of this technique have been devised in order to further protect OARs and/or to improve positional breast reproducibility and stability during successive short and voluntary apneas. Breath-hold induced by mechanically-assisted and non-invasive ventilation (MANIV-DIBH) could potentially combine these optimizations: a pressure-controlled ventilation mode whose breathing parameters remain identical over time would reach higher and more reproducible lung inflation levels than those obtained with standard DIBH. The objective of this study is to confirm in real-life radiotherapy treatment that breast position reproducibility/stability with MANIV is at least non-inferior to that of voluntary DIBH guided by surface imaging (sDIBH) while better protecting critical OARs with respect of patients’ comfort. Materials and Methods The study is designed as a randomized, non-blinded, prospective, monocentric trial comparing sDIBH and MANIV-DIBH for left breast tumor without lymph node invasion during irradiation. In the standard arm, patients are asked to hold a DIBH for 20 seconds during which left breast position is guided and monitored by an operator using a surface imager. In the interventional arm, patients are connected to a mechanical ventilator reproducing apneas by alternating two pressure levels with oxygen enriched air (FiO2 60%). Primary endpoint corresponds to the positional breast reproducibility and stability. Stability refers to the average intra-plateau shifts, while reproducibility corresponds to the mean breast deviation relative to daily reference breast surface. Secondary endpoints are the following: dose to critical OARs, DIBH duration, comfort level and treatment time. Results Since July 2020, 25 patients have been included. Flow chart presented in figure 1 summarizes actual state of data processing for results presented hereafter. As shown in table 1, difference between both arms for positional breast reproducibility and stability occurred at a submillimetric level. Trend towards a better lung protection and a significantly better cardiac dosimetric sparing were noticed with MANIV-DIBH. A significantly higher lung inflation and larger reduction in cardiac volume were reached in the interventional arm. By contrast, only slight differences in terms of tolerance and treatment time were observed between both DIBH modalities. Finally, no adverse event nor abnormal vital parameters values (heart rate, Sp0 2 ,etCO 2 ) were recorded with mechanical ventilation.