ESTRO 2021 Abstract Book

S1171

ESTRO 2021

sarcoma B. Guerrieri 1 , C. Mattioli 1 , M. Loi 1 , D. Greto 1 , M. Ganovelli 1 , G. Frosini 1 , V. Lorenzetti 1 , C. Cerbai 1 , D.A. Campanacci 2 , G. Roselli 3 , A. Palomba 4 , A. Tamburini 5 , L. Livi 1 1 University of Florence, Radiation Oncology Unit, Florence, Italy; 2 University of Florence, Department of Orthopaedic Oncology and Reconstructive Surgery, Florence, Italy; 3 University of Florence, Azienda Ospedaliera Universitaria Careggi, Florence, Italy; 4 University of Florence, Section of Pathological Anatomy, Department of Health Sciences, Florence, Italy; 5 Meyer University Children's Hospital, Division of Pediatric Oncology/Hematology, Florence, Italy Purpose or Objective Ewing sarcoma (EWS) is a rare malignancy with a high metastatic potential. The most common genetic abnormality is 22q12 translocation, found in 90% of cases. However, the prognostic role of chromosomal abnormalities as driver factors in the clinical course of the disease is still investigational. Here we present a retrospective analysis on the outcome of non-metastatic Ewing patients treated with neoadjuvant chemotherapy followed by local treatment. Materials and Methods We present a retrospective review of cases treated in our institution from April 2002 to July 2019. Presence of 22q11 rearrangement was detected with Fluorescent in situ hybridization (FISH). We performed a statistical analysis to assess the predictive correlation of clinical and genetical features on Distant Metastasis-Free Survival (DMFS) and Overall Survival (OS). Results Data from 27 non-metastatic EWS patients were included. Skeletal and extraskeletal disease was observed in 20 (74%) and 7 (26 %) patients, respectively; 22q12 translocation was present in 22 cases (81%), while lack of translocation was found in 5 cases (19%). Primary tumor location affected the trunk in 48% of cases (n=13) and the limbs in 52% of cases (n=14). All patients received upfront chemotherapy according to the ISG/SSGIII and the ISG/AIEOP-EWS1 protocol in 18 (66%) and 9 (34%) cases, respectively, followed by local treatment of the primary tumor. Surgery was performed in 24 patients (88%), resulting in a 87% R0 resection rate (n=21): a Picci grade 3 complete response was observed in 20% (n=5) of tumor specimens. Preoperative or postoperative irradiation was delivered in 5 (19%) and 7 (26%) cases, respectively, while 3 (11%) patients received definitive radiotherapy to a dose of 54 Gy in 36 fractions. Total Lung Irradiation (TLI) delivering 15 Gy in 10 fractions was performed in 4 patients (15%). After a median follow-up of 23 months (range 9-73 months), metastatic relapse occurred in 9 patients and 4 patients died of disease. DMFS was 96% at 1 year and 73% at 2 years; OS was 96% at 1 and 2 years. Absence of 22q12 translocation was the only feature significantly associated with impaired DMFS (median 18 months versus not reached, p=0.005) and OS (median not reached, p=0.038).