ESTRO 2020 Abstract book

S591 ESTRO 2020

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 oncological outcomes in patients with BMs from NSCLC, treated with SRS and TKIs or IO. Material and Methods A total of 195 patients with synchronous and metachronous BMs from NSCLC treated with CyberKnife radiosurgery

(CKSRS) and concomitant pre- or post-systemic therapy were analyzed. Exclusion criteria included prior wall brain radiotherapy (WBRT), surgery removal of BMs, prior SRS on the same lesion or insufficient follow-up. The primary endpoint was distant brain failure (DBF). DBFs were defined as any new metastases that developed outside of the previous radiosurgical target volume. Time to DBF was calculated from the start of SRS to DBF. Overall Survival (OS) was the secondary endpoint. We stratified our cohort of patients with Modified Lung Specific Prognostic assessment (GPA) in three prognostic cathegories and subsequently the impact of mutation on OS was tested for each category. Results Median time free from DBF for our patients cohort was 15.3 months (95% CI 11.6-20.4). No statistically significant differences were found between the mutated and not mutated patients (p-value 0.414). For the cohort of patients with the PDL-1 expression (N= 41), no statistically significant differences were found in DBF (p-value 0.371). Considering free from DBF at 12 months (Fig.1), we observed a better trend for patients with expression of PDL-1>1%, 50.6% (95% CI 30.1-68.0), compared to patients without PDL-1 expression (<1%), 31.2% (95% CI 8.1- 58.2). Median OS was 19.9 (95% CI 15.1-27.4) months; no statistical significant differences in OS were noted in patients with targetable mutations (p-value 0.110), even if there was a trend in favor of mutated patients. For patients included in prognostic GPA<2 category we obtained a statistical significative difference in OS (p- value 0.026) in favor of patients with targetable mutations (Fig.2). Conclusion This mono-institutional analysis demonstrates that targetable mutations do not influence the locoregional control of the patients treated with SRS. Otherwise, for patients with altered immune system state, potential benefits in oncological outcomes could be represented by association of SRS with immune-modulatory therapies. For patients with a worse expected prognosis (GPA<2), the presence of targetable mutations seems to improve OS. Of notes we need to confirm these data with a larger and prospective cohort of patients, but our findings represent an encouraging hypothesis generating findings to select patients who benefit for personalized treatments. PO-1024 Fractionated RT is equally effective but less toxic than SBRT for central early-stage NSCLC M. Leenders 1 , S. Peeters 1 , J. Van Loon 1 , A. Van Baardwijk 1 , B. Reymen 1 , K. Verhoeven 1 , M. Öllers 2 , R. Wanders 1 , D. De Ruysscher 1 1 Maastro, Radiotherapy, Maastricht, The Netherlands ; 2 Maastro, Physics, Maastricht, The Netherlands Purpose or Objective Stereotactic body radiotherapy (SBRT) for central early stage non-small cell lung cancer (NSCLC) is reported to lead to 5-25% grade 5 toxicities, mainly bleeding (Tekatli Radiother Oncol 2015, JTO 2016). We hypothesized that a more fractionated accelerated regimen would be as effective as SBRT (van Baardwijk Radiother Oncol 2012), but less toxic. Material and Methods Stage I NSCLC patients were included between July 2012 and January 2019. Pathological confirmation was not mandatory. Systemic anti-cancer treatment was not allowed. All patients were staged with a whole body FDG- PET-CT scan. RTOG definition of a central lung tumor was used: “Tumor within or touching the zone of the proximal bronchial tree, defined as a volume of 2 cm in all directions around the proximal bronchial tree. Tumors that are immediately adjacent to mediastinal or pericardial pleura (PTV touching the pleura) were also are considered central tumors”. The treatment was delivered in 24 daily fractions of 2.75 Gy (For tumor: EQD2=71 Gy, EQD2,T=69