ESTRO 2023 - Abstract Book

S1352

Digital Posters

ESTRO 2023

Conclusion The obtained results of the ipsilateral lung transferability and dose/statistical prediction, support the possibility to use LWB-TF FB models for the prediction of LWB-TF DBHI candidates. Heart transferability and dose/statistical prediction should be considered with caution, with most free breathing models showing only moderate transferability. Importantly, the INST1DIBH model was fully transferable on DIBH patients of other Institutes

PO-1652 KB multi-institutional plan prediction of the left whole breast irradiation with tangential fields

R. Castriconi 1 , A. Tudda 1,2 , G. Benecchi 3 , E. Cagni 4 , F. Dusi 5 , A. Ianiro 6 , V. Landoni 6 , T. Malatesta 7 , A. Mazzilli 3 , G. Meffe 8 , C. Oliviero 9 , L. Placidi 8 , G. Rambaldi Guidasci 7 , A. Scaggion 5 , V. Trojani 4 , C. Fiorino 10 1 IRCCS San Raffaele Scientific Institute, Medical Physics Department, Mian, Italy; 2 Università Statale di Milano, Physics Department, Milan, Italy; 3 University Hospital of Parma AOUP, Medical Physics Department, Parma, Italy; 4 Department of Advanced Technology, Azienda USL-IRCCS di Reggio Emilia, Medical Physics Unit, Reggio Emilia, Italy; 5 Veneto Institute of Oncology IOV–IRCCS, Medical Physics Department, Padua, Italy; 6 IRCCS Istituto Nazionale dei Tumori Regina Elena, Medical Physics, Rome, Italy; 7 Fatebenefratelli Isola Tiberina - Gemelli Isola, UOC di Radioterapia Oncologica, Rome, Italy; 8 Fondazione Policlinico Universitario Agostino Gemelli IRCCS, UOSD Medical Physics and Radioprotection, Rome, Italy; 9 University Hospital, “Federico II”, Medical Physics , Naplse, Italy; 10 IRCCS San Raffaele Scientific Institute, Medical Physics Department, Milan, Italy Purpose or Objective Whole-breast irradiation with tangential fields (TF) is still a largely used technique in post-operative radiotherapy of breast cancer. The expected consistency in contouring and plan techniques together with the high number of treated patients may translate into knowledge-based (KB) models usable on a large scale. In the context of a multi-institutional project, we already demonstrated the transferability of KB-models for the right-breast TF irradiation. Aims of the present study were to evaluate inter-institute KB-model’s variability and transferability also in the case of the left-breast irradiation. Materials and Methods Eight institutions set KB models by using RapidPlan (Varian Inc.), following previously shared methodologies. The plan prediction performances of the resulting models were tested on 16 randomly chosen additional patients (pts), available at the time of the investigation (2 pts per centers). All models were run considering the most used scheme, delivering 40Gy/15fr. DVH prediction bands of OARs (heart, ipsilateral lung, contralateral lung and contralateral breast) were analyzed. The inter-institute variability was quantified by the inter-institute SD of predicted DVHs/Dmean. The transferability of models among institutes, for the heart and the ipsilateral lung, was evaluated by the overlap of the geometric Principal Component (PC1) when applied to the test patients of the other 7 institutes. This parameter was previously assessed as robustly representative of the association between anatomy/segmentation and DVH prediction of OARs, in quantifying if a model can be reasonably applied to patients scanned and segmented in other Institutions.