ESTRO 2021 Abstract Book

S354

ESTRO 2021

Conclusion Compared to VMAT, VHEE plans could strongly reduce OAR and patient doses and enhance plan conformality for similar PTV doses. Reductions in OAR and patient doses increased with increasing electron beam energy and beam number. OC-0468 Implementation of a Knowledge-Based automated approach for whole breast tangential field planning P.G. Esposito 1 , R. Castriconi 1 , P. Mangili 1 , S. Broggi 1 , A. Fodor 2 , B. Longobardi 1 , M. Pasetti 2 , L. Perna 1 , N. Di Muzio 2 , A. Del Vecchio 1 , C. Fiorino 1 1 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Radiotherapy, Milan, Italy Purpose or Objective To implement a Knowledge-Based (KB)-automatic planning approach for right-sided (R) and left sided (L) whole breast treatment using a new volumetric technique ViTAT (Virtual Tangential Arc Therapy) that mimics conventional Tangential Field (TF) irradiation Materials and Methods We selected R:80/L:90 TF clinical plans to train two KB-models for R and L sided patients using the RapidPlan (RP) tool implemented in the Eclipse TPS (v13.6, Varian Inc.). As RP needs RapidArc (RA) plans to build accurate DVH prediction, based on the association between dosimetry and delineated structures features, TF dose distributions were first linked to virtual RA-plans. The resulting KB-models were interactively fine-tuned in terms of statistical DVH-estimation and translated into templates for ViTAT automatic optimization, aiming at maximizing their robustness. ViTAT plans consisted of 4 arcs (6MV) optimized with a RA technique with start/stop angles consistent with TF geometry (R:60°/220° L:300°/135°); arcs were completely blocked, apart the first and last 20° of rotation. Validation tests on 60 patients, equally divided between R/L-sided plans, were performed to assess the performances of models. All KB fully-automatic ViTAT-plans (KB-ViTAT) were compared against the original plans (TF) in terms of OARs/PTVs dose-volume parameters. Wilcoxon-tests were performed to assess statistically significant differences (p<0.05).