ESTRO 2020 Abstract Book

S545 ESTRO 2020

PO-1022 Clinical-dosimetric assessment with Prodvh software after adjuvant radiotherapy for MPM E. Salah ElDin Tantawi 1 , P. Borghetti 1 , C. Cozzaglio 2 , M. Bonù 1 , N. Pasinetti 1 , D. Greco 1 , M. Maddalo 1 , A. Baiguini 1 , P. Vitali 1 , E. Ranghetti 1 , A. Guerini 1 , M. Buglione 1 , L. Spiazzi 2 , S.M. Magrini 1 1 Spedali Civili di Brescia, Istituto del Radio, Brescia, Italy ; 2 Spedali Civili di Brescia, Medical Physics, Brescia, Italy Purpose or Objective To analyze overall survival (OS), acute and late lung toxicity in a retrospective cohort of patients undergoing adjuvant radiotherapy after extra-pleural pneumonectomy (EPP) for malignant pleural mesothelioma (MPM), with or without chemotherapy. To investigate possible correlations between dosimetric data and clinical outcomes and assess the role of 3 dimensional conformal RT (3DCRT) and intensity modulated RT (IMRT) in terms of coverage of target volumes and preservation of the major organs at risk (esophagus, lungs, heart). Material and Methods Data of all patients (pts) treated with adjuvant RT after EPP for malignant pleural mesothelioma were reviewed. Overall survival (OS), acute and late lung toxicity (ALT and LLT) according to CTCAE V4.0 scale were analysed. Kaplan- Meyer curves and log-rank test were used for survival analysis, while chi-square test was calculated to compare the different variables. P< 0.05 was considered significant. Furthermore, the data of all patients were evaluated with PRODVH, a homemade software developed to compare biologically equivalent DVHs and calculate mean DVH within clinically relevant groups (type of treatment, technique used, OAR and PTV) Results From 2005 to 2013 58 patients were treated with adjuvant RT after EPP for malignant pleural mesothelioma. The 3, 5 and 8 years overall survival rates resulted to be 48%, 34% and 18% respectively. Our study confirmed the relevant contribution of IMRT to local control after EPP. Local relapse free survival resulted to be 80%, 64% and 58% at 3, 5 and 8 years, respectively. Analysis of PRODVH showed that worse DVHs of OARs (lung, left coronary artery, pericardium and heart) are related with an increased risk of toxicity, in particular dyspnea. Conclusion IMRT following EPP achieved excellent local control for MPM, that might lead to the long-term survival in selected patients. However, treatment burden including acute and late toxicities should be considered in this treatment approach. Single plan DVH does not represent by itself the best approach to estimate treatment-related toxicity. PRODVH produces an average DVH giving more accurate information on the dosimetric features related with an increased risk of toxicity. PO-1023 Impact of biological features in radiosurgery for Brain metastases from Non Small Cell Lung Cancer S. Durante 1 , G. Corrao 1 , G. Marvaso 1 , G. Piperno 1 , F. Colombo 1 , S.G. Gugliandolo 1 , E. Rondi 1 , S. Vigorito 1 , S. Frassoni 2 , V. Bagnardi 2 , C.I. Fodor 1 , L. Spaggiari 1 , F. De Marinis 1 , R. Orecchia 1 , B.A. Jereczek-Fossa 1 1 European Institute of Oncology- IRCCS, Radiation Oncology, Milan, Italy ; 2 University of Milano Bicocca, Department of Statistics and Quantitative Methods, Milano, Italy Purpose or Objective Stereotactic radiosurgery (SRS) and tyrosine kinase inhibitors (TKIs) are the standard options for patients with brain metastases (BM) from non-small cell lung cancer (NSCLC) who arbor targetable mutations (EGFR and ALK). For the others patients, immunotherapy (IO) is an emerging treatment. This mono-institutional analysis aimed to determine the influence of mutations on

statistically significant differences were observed between MR and planning CT contours. Conclusion These results highlight the limitation of CBCT images for daily online replanning in thoracic tumours. Though our results need to be validated with on-board MR-images, they suggest that there could be clear advantages to using daily MR-guided radiotherapy for cardiac SABR, where precise delivery of radiotherapy would result in optimal dose whilst minimising risk of complications. Further investigation is needed to determine the best MR sequences required for daily MR-based adaptive replanning for cardiac SABR. PO-1021 Stereotactic radiotherapy for unresectable locally advanced non small cell lung cancer F. Arcidiacono 1 , P. Anselmo 1 , F. Trippa 1 , M. Casale 1 , M. Italiani 1 , L. Draghini 1 , S. Terenzi 1 , S. Fabiani 1 , A. Di Marzo 1 , E. Maranzano 1 1 Radiotherapy Oncology Centre, Santa Maria Hospital, Terni, Italy Purpose or Objective Conventional fractionated radiotherapy (cRT) concurrent with chemotherapy (ChT) is the standard of care in unresectable locally advanced non small cell lung cancer (LA-NSCLC).The majority of patients (pts) cannot tolerate this treatment due to its toxicity, so sequential ChT followed by cRT is the more frequent choice in clinical practice. Recently, stereotactic radiotherapy (SBRT) has been used instead of cRT in NSCLC offering superior control with less toxicity. We present our experience with SBRT in LA-NSCLC. Material and Methods Between June 2015 and April 2019, 30 LA-NSCLC pts who underwent SBRT were analyzed . 24/30 (80%) pts received neoadjuvant ChT before SBRT. All pts had CT-PET before SBRT. In pts submitted to neoadjuvant ChT the target volume was the residual disease defined on the basis of CT-PET images. The technique was intensity modulated arc therapy(IMAT) and volumetric modulated arc therapy (VMAT) in 14(46%) and 16 (54%) pts, respectively. A specific treatment planning (IMRT-SIB) for primary tumor (T) and lymph-node/s (N) was done for 16(53%) pts, while in remaining 14(47%)the planning target volume (PTV) included both T and N. All pts repeated CT-PET 3 months after treatment and thereafter every 4-6 months. The toxicity was evaluated using CTCAE scale. Results Median age was 73 years (54-86). 9(30%), 15(50%) and 6(20%) pts had clinical N1, N2 and N3 stage at diagnosis, respectively. 27 (90%) and 3 (10%) had central and peripheral primary tumor. Median PTV for T and N separately treated were 58.07 cc (8.7-673) and 15.02cc (5.84-72.3), while for T and N treated in the same target was 105.15 cc (53.2-733). Median prescribed dose was 40 Gy (35-55) and 40 Gy (35-45) in 5 fractions to T and N, respectively.After a median follow-up of 12 months (4-51) 7 of 30 (23%) pts had local recurrence (LR), 9 (30%) regional node (RN) recurrence and 10 (30%) distant progression (DP). Median LR free survival (FS), RN-FS and DP-FS were 9 months (4-48), 9 months (4-48) and 9 months (4-48), respectively. Median overall and cancer specific survival were 12 months (4-48). Of note 2 patients who had hemoptysis before SBRT resolved the symptom after treatment. No patients developed > grade 2 toxicity. Conclusion SBRT was a feasible,safe and effective treatment in selected unresectable LA-NSCLC pts. Although clinical outcomes were very promising both in terms of results and toxicity,larger and more mature studies are needed to adopt this treatment in clinical practice.