ESTRO 2023 - Abstract Book

S104

Saturday 13 May

ESTRO 2023

Conclusion Target volume delineation according to the new ESTRO-ACROP guideline did not reduce the risk of major or any breast- related complications. As the dosimetric benefits of heart and lung have been reported, further analyses with long-term follow-up are necessary to evaluate whether it could be connected to better clinical outcomes. MO-0142 Implementation of mechanical ventilation for left breast cancer: final results of a randomized trial L. Vander Veken 1 , G. Van Ooteghem 1 , A. Razavi 2 , S. Da Rita Quaresma 2 , E. Longton 2 , C. Kirkove 2 , B. Ledoux 2 , A. Vandermeulen 2 , C. Abdel Massih 2 , P. Henderickx 2 , M. Gabriels 2 , C. Delvaux 2 , F. Salah 2 , A. Vaandering 2 , X. Geets 2 1 Institut de Recherche Experimentale et Clinique (IREC), Center of Molecular Imaging, Radiotherapy and Oncology (MIRO), Université Catholique de Louvain, Brussel, Belgium; 2 Cliniques Universitaires Saint-Luc, Radiation Oncology, Brussel, Belgium Purpose or Objective In the context of adjuvant left breast radiotherapy, collateral cardiac irradiation is associated with increased cardiovascular morbidity. By reducing the heart and the ipsilateral lung doses, deep inspiration breath-hold (DIBH) has thus become a standard-of-care. Different strategies have been developed either to optimize the breast repositioning accuracy during successive DIBH e.g. surface guided radiation therapy (SGRT) and/or to improve organs-at-risk (OARs) sparing e.g. prone position, continuous positive airway pressure (CPAP). These DIBH enhancements can potentially be coupled by mechanically-assisted and non-invasive ventilation (MANIV). Indeed, MANIV allows DIBH to be faithfully replicated with a large lung inflation by periodically imposing the same positive pressure for a predefined duration. The objective of the present study was therefore to test our research hypothesis by comparing, in real treatment conditions, voluntary DIBH guided by SGRT and MANIV-induced DIBH in supine position. Materials and Methods A randomized, non-blinded, multicenter and single-institution non-inferiority trial was conducted (NCT04457102 on ClinicalTrials.gov). Sixty-six patients eligible for adjuvant left whole-breast radiotherapy in supine position were assigned in a (1:1) ratio between mechanically-induced DIBH (MANIV-DIBH arm) and voluntary DIBH guided by SGRT (sDIBH arm). The study flow chart is shown in Figure 1. In the sDIBH arm, treatment beam was delivered in 20 seconds DIBH during which the patient received oral instructions from the operator to adjust the breast position based on SGRT. In contrast, the breast position was simply monitored by SGRT in the MANIV-DIBH arm. The treatment worflow of the MANIV-DIBH arm is illustrated in Figure 2. The co-primary endpoints were positional breast stability and reproducibility with a non-inferiority margin of 1 mm. Stability corresponded to the average intra-DIBH shifts, while reproducibility referred to the mean breast deviation during DIBH relative to a daily reference breast surface. Secondary endpoints were dose to OARs, tolerance and treatment time. Given the use of different fractionation schedules within the study, dosimetric comparisons was performed on treatment plans with a prescription of 15 x 2.67 Gy without boost.