ESTRO 2020 Abstract book

S615 ESTRO 2020

patient), statistical analysis was not performed. One-year PFS was 35% (CI 95%: 17-57%, median 9 months): only TTR ≥24 months was correlated to improved PFS (16 vs 6 months, p=0.036). One-year OS was 74% (95% CI:51-88 %, median 17 months): neither clinical nor treatment related variable was correlated to improved OS . Four patients (19%) experienced G1-2 acute nausea. No grade 3 and 4 toxicity were reported

Conclusion Higher post CA19-9 was significantly associated with inferior OS and PFS in patients with BR or UR pancreatic adenocarcinoma receiving CRT. Post CA19-9 might be useful to predict the early recurrence after CRT. PO-1072 Stereotactic radiotherapy in liver metastases of mesenchymal malignancies: role of patient selection L. Di Brina 1 , M. Loi 1 , T. Comito 1 , P. Navarria 1 , C. Franzese 1 , E. Clerici 1 , D. Franceschini 1 , F. Lobefalo 1 , S. Tomatis 1 , P. Mancosu 1 , M. Scorsetti 1 1 Humanitas Research Hospital, Radiotherapy and Radiosurgery, Rozzano Milan, Italy Purpose or Objective STS are a heterogeneous and rare group of mesenchymal malignancies of connective tissue usually of the extremities. GIST are rare mesenchymal tumors of the gastrointestinal tract. In these patients, liver metastases are an unfrequent occurrence that may benefit of a local approach. Radiation therapy (RT) for metastatic STS or GIST has historically been limited to palliation due to presumed radioresistance. However, delivery of highly focused ablative irradiation through Stereotactic Radiotherapy (SBRT) may be effective in obtaining disease control.The aim of our study was to evaluate the feasibility, efficacy and toxicity of SBRT for treating unresectable hepatic metastasis in patients affected by mesenchymal malignancies. Material and Methods Medical records of patients treated at your Institution with SBRT for liver metastases from sarcoma or GIST Between 2010 and 2018 were retrospectively reviewed. Biological Effective Dose (BED) was calculated to compare different dose regimens. Local Control (LC), Progression-Free Survival (PFS) and Overall Survival (OS) were calculated from the date of SBRT using the Kaplan Meyer method. Toxicity was record and scored according to the Common Terminology Criteria For Adverse Events (CTCAE v 4.03) Results Twenty-one patients accounting for 26 metastases were included. Histotype was soft tissue sarcomas and GIST in 16 (77%) and 5 (23%) cases respectively. Median time from primary treatment to disease relapse (TTR) was 19 (1-85) months. Primary site was controlled in 19 (90%) patients. Extra-hepatic sites of disease were present in 6 (28%) cases. Nine patients (43%) were chemotherapy-naïve at the time of SBRT. Median BED of SBRT was 134 (58-263) Gy 10 . Median follow-up was 16 (range 3-55) months. LC rates at 1 year was 84% (CI95% 62-94%, median not reached): due to small number of events (n=3, same

Conclusion SBRT for metastatic lesions is feasible and effective with good local control rates in liver metastases of mesenchymal derivation. Due to poor PFS in relation to occurrence of extrahepatic metastases, patient selection should take into account time from primary treatment to relapse among criteria for decision to perform SBRT. PO-1073 Dosimetric Predictors of Survival in Esophageal Cancers Treated with Preoperative Chemoradiation S. Garcia 1 , A. Tavares 2 , P. Peixoto 1 , F. Costa 1 , D. Saraiva 1 , P. Varzim 1 , A. Monteiro 1 , M.P. Fontes 1 , G. Pinto 1 1 Centro Hospitalar Universitário São João, Radiation Oncology, Porto, Portugal ; 2 Hospital Pedro Hispano, Medical Oncology, Porto, Portugal Purpose or Objective Esophageal cancers (EC) constitute a major global health problem, with a high mortality rate. Preoperative chemoradiation (CRT) is the preferred approach for localized disease, as it improved overall survival (OS), disease free survival and pathological complete response compared with preoperative chemotherapy or surgery alone. Recently, high heart and lung doses have emerged as potential indicators of a worse outcome in this patient group. The present retrospective study aims to analyse whether there is a correlation between the heart and lung dose and OS in patients with esophageal cancer who received preoperative chemoradiotherapy. Material and Methods This study included patients with EC treated with preoperative CRT, with or without surgery, between January 2008 and September 2018 in a Portuguese institution. All patients were treated with 3DCRT to a total dose of 45Gy given in 1.8Gy fractions. Dose-volume histogram’s data were extracted from Xio or Eclipse treatment planing systems, and the following dosimetric variables were computed: mean heart dose (MHD), mean lung dose (MLD), heart V15-50 (in 5Gy