Oral Etoposide for Relapsed or Refractory Ewing Sarcoma in Adolescent and Adult Patients

Prognosis remains poor for patients with relapsed or refractory Ewing sarcoma, with limited treatment options after first-line therapy. Oral etoposide has efficacy in the paediatric setting; however, data are limited in adults. A retrospective analysis was conducted on 33 patients with relapsed or refractory Ewing sarcoma who completed at least one cycle of oral etoposide at the Peter MacCallum Cancer Centre from 2005 to 2020. The median age at diagnosis and first relapse was 21 and 23 years, respectively. All patients had prior exposure to intravenous etoposide. Nine patients (27%) had stable disease for at least 6 months, and six patients (18%) had a partial response. The clinical benefit rate was 45%. The median PFS was 3.6 months (95% CI: 1.7-5.5), and OS was 8.5 months (95% CI: 4.1-13.0). Despite prior exposure, oral etoposide demonstrated antitumour activity and durable responses in the relapsed or refractory setting for adult patients with Ewing sarcoma.