1523P - Efficacy of second line treatment with etoposide and ifosfamide in adult patients with advanced Ewing Sarcoma family tumors

Abstract

Background: Ewing Sarcoma family tumors (ES) are rare subtypes of sarcomas, and even less common in adult patients. For those not amenable to treatment with curative intent, sequential therapy with multi-agent combinations is the standard of care, usually followed by ifosfamide/etoposide (IE) at the time of progression, largely based on protocols that included pediatric patients. Nevertheless, less is known about the efficacy of this approach for adult patients with ES refractory to first-line therapy. Methods: We assembled a retrospective cohort of patients aged 18 or older diagnosed with metastatic/inoperable ES refractory to first-line combinations, treated with IE between 2010 and 2016. Patient´s characteristics, tumor variables, treatment outcomes and toxicity data were evaluated. Kaplan-Meier method was used to estimate overall survival and uni/multivariate analysis were carried out to identify factors associated with survival. Results: Among 18 adult patients, the mean age of diagnosis was 22 years, 73% were male and 84% had an ECOG of 0-1 at commencement of IE. Pelvis and thorax were the most common primary sites. The mean number of cycles of IE was 4. The disease control rate was 27%, with partial responses occurring in 16% of the patients (there were no complete responses). The median OS was 4,8 months (IC 95% 0,7-8,8). Toxicities ³ grade 3 occurred in 61% of the patient, including two treatment-related deaths. The main grade 4 toxicity was febrile neutropenia. Hospitalization were required in 55% of the cases. Conclusions: IE has limited efficacy and significant toxicity when used in the second-line setting for adult patients with advanced ES, and different approaches should be investigated for these patients. Legal entity responsible for the study: Instituto do Câncer do Estado de São Paulo Funding: None Disclosure: All authors have declared no conflicts of interest.