Primary Mediastinal Ewing's Sarcoma: Post Hoc Analysis from Two International Multicenter Prospective Randomized...

Ewing sarcoma (EWS) of the mediastinum is extremely rare, with only a few cases reported in the literature. We aimed to gain a better understanding of primary mediastinal EWS, describing patients treated within two international, multicenter, prospective, randomized EWS trials.

Data from patients with primary mediastinal EWS were retrieved from the database of the EURO-E.W.I.N.G.99 (ClinicalTrials.gov identifier: NCT00020566) and EWING 2008 (ClinicalTrials.gov identifier: NCT00987636) trials. Patient and treatment characteristics were analyzed.

Out of 2969 patients with EWS, 9 (0.3%) had primary mediastinal EWS. The median age at diagnosis was 30.5 years (4 to 49). At the time of diagnosis, n = 3 (33%) patients had synchronous metastases. All patients underwent multiagent chemotherapy. Local therapy for non-metastatic patients was surgery (n = 2, 22%), surgery and radiotherapy (n = 2, 22%) or radiotherapy alone (n = 2, 22%). Surgery consisted of extended resections in most patients (n = 3, 33%). Five-year survival for the whole cohort was 64%. Apart from one patient who was lost to follow-up, all patients (n = 4) who had undergone surgery were alive at the end of follow-up.

Primary mediastinal ES is extremely rare, with a prevalence of 0.3% among EWS. Five-year survival was favorable compared to primary mediastinal sarcoma of all histologies and in line with EWS of different origin.