ESTRO 2020 Abstract book

S696 ESTRO 2020

PO-1232 Patients with pelvic Ewing Sarcoma with metastases at time of diagnosis: a monocentric experience L. Ronchi 1 , S. Cammelli 1 , B. Spazzoli 2 , M. Manfrini 2 , M.E. Abate 3 , A. Longhi 2 , A.G. Morganti 1 , D.M. Donati 2 1 Radiation Oncology Unit, Department of Experimental- Diagnostic and Specialty Medicine- S. Orsola-Malpighi Hospital-, Bologna, Italy ; 2 Istituto Ortopedico Rizzoli- Bologna- Italy., Departments of Orthopaedic Oncology-, Bologna, Italy ; 3 AORN Santobono-Pausilipon, Oncologia Pediatrica, Napoli, Italy Purpose or Objective Pelvic Ewing sarcoma with metastases at time of diagnosis is a rare event with severe prognosis. We retrospectively reviewed our experience in order to identify outcomes of this subgroup of patients. Material and Methods Twenty-seven patients (pts) (male/female 18/9; median age 20.7 years; range 8-38 years) treated at our institution from 2005 to 2015 were included in the study. Median follow up was 23 months (range 1-112). At time of diagnosis 14 pts (52%) had lung metastases, 7 pts (26%) had bone metastases, 6 pts (22%) had both. In 23 patients (85%) tumor volume was larger than 200 ml. All patients received standard chemotherapy (CHT) and 10 pts (37%) had standard and high dose CHT. Local treatment on primary tumor was exclusive Radiotherapy (RT) in 20 pts (74%) and RT + surgery in one pt (4%). Median RT dose was 54Gy. Six pts (22%) died before the beginning of local treatment. Median interval time from diagnosis to RT treatment was 5 months. Results 23 pts (85%) died of disease: 12 (44%) had progressive disease during chemotherapy, while other 11 pts (41%) died after an average time of 12 months from the end of chemotherapy (range 2-22) with controlled disease until that time. Four (15%) out of 27 pts are still alive with no evidence of disease: one pt had a small primitive tumor (< 200 ml), while the other 3 pts received intensification of local therapy with a stable disease 12 months after the end of CHT : 1 had surgery on primitive tumor in iliac wing at the end of chemotherapy, 1 had surgical excision of lung metastases and the 1 had surgery + stereotactic RT on brain metastases. Conclusion Long survivor patients had small tumor or intensive metastases treatment. Based on this trend, we suggest an intensification of cures (both RT and surgery on the residual tumor) in patients who had a stable disease 12 months after the end of CT. PO-1233 Perioperative Radiotherapy with a Moderate Dose-Escalation for Retroperitoneal Sarcoma (RPS). M. Nuñez Baez 1 , A. Montero 1 , X. Chen-Zhao 2 , A. Acosta 1 , B. Alvarez 1 , J. Palma 1 , M. Lopez-Gonzalez 1 , E. Sanchez 1 , O. Hernando 2 , J. Valero 1 , R. Ciervide 1 , M. Garcia-Aranda 1 , R. Alonso 1 , M. De la Casa 3 , D. Zucca 3 , J. Martí 3 , I. Flores- Cacho 3 , C. Ruiz-Morales 3 , P. Fernandez-Leton 3 , M. Rubio Rodriguez 1 1 HM Sanchinarro, Radiation Oncology, Madrid, Spain ; 2 HM Puerta del Sur, Radiation Oncology, Madrid, Spain ; 3 HM Sanchinarro, Radiophysics, Madrid, Spain Purpose or Objective Although surgery represents the main primary therapeutic approach for RPS, it carries several risks related to vital structures located in a complex space. The purpose of our study is to assess the outcome and toxicities of patients with RPS. Material and Methods We included 19 patients with diagnoses of RPS treated between November/2009- November/2018. Sex: male 9p (47%); female 10p (53%). Median age: 55y (range 36-68). Presentation: primary 14p (74%); relapsed 5p (26%).

Fight Against Cancer (Federation Nationale des Centres de Lutte Contre le Cancer; FNCLCC). Surgical margins, primary tumor sites, treatment-related toxicities and other clinical characteristics were also investigated. Results Median patient age was 85 years (range, 80–92). All 28 cases were histologically categorized as grade 3 by FNCLCC and stage III disease (based on 8th cancer staging manual by American Joint Committee on Cancer, AJCC). Among the 28 patients, 10 has primary DDLPS in retroperitoneum and 18 in trunk/extremities. Median follow-up was 46.9 months (range, 3.7–115.1). 10 patients (35.7%) received concurrent chemotherapy. Local recurrence occurred in eight (28.6%), distant metastasis in seven (25%), and both in six (10.7%) patients. The 2-year and 5-year OS rates were 80.5% and 61.1%. The 2-year and 5-year DFS rates were 63.5% and 47.6%. A log-rank test showed longer 5- year DFS in the patients with negative resection margin than positive resection margin (64.7% vs. 38.9%, P<0.02). Primary tumor site, age, gender, radiation dose and the administration of concurrent chemotherapy were found to be not correlated to DFS and OS. Acute toxicities grade ≤2 were observed in 71.4% of patients and no acute toxicity ≥grade 3 occurred.

Conclusion To the best of our knowledge, this is the first study to date focusing on patients of DDLPS with advancing age. Negative resection margin was found to be associated with higher 5-year DFS rate. 5-year OS rate (61.1%) was observed despite the aggressive liposarcoma subtype, high histological grade and cancer staging. Adverse events are uncommon. However, due to the scarcity of patient data, the appropriate selection of radiotherapy in this disease remains challenging. The optimal adjuvant management of DDLPS among elderly patients requires further study.