Intensified Induction Therapy for Newly Diagnosed, Localized Skeletal Ewing Sarcoma (ISG/AIEOP EW-1): A Randomized, Open-Label, Phase 3, Non-Inferiority Trial.

Background: Several studies have shown that the intensity of treatment in Ewing sarcoma has an impact on outcome. The present trial tested the non-inferiority of intensive, shorter, induction chemotherapy (25 weeks total treatment time) compared to the standard treatment (37 weeks) in non-metastatic Ewing sarcoma (ES) at onset.

Procedure: This national, multicenter, parallel, randomized, controlled, open-label, non-inferiority, phase III trial was conducted in 14 specialized hospitals in Italy. Patients aged 2-40 years with newly diagnosed localized ES were randomized to receive four courses of induction therapy (one every 21 days) either with a standard arm (Arm A) or with an intensive arm (Arm B). For consolidation therapy, good responders (GRs) in Arm A received nine courses (37 weeks), while Arm B patients received five courses (25 weeks). Poor responders for both arms received four courses followed by high-dose busulfan/melphalan + autologous stem cell rescue. Follow-up was 5 years.

Results: In the study period 2009-2018, 274 patients with ES at onset were screened, 248 were eligible, 15 refused randomization, and 233 were randomized (Arm A: 113; Arm B: 120). Median age was 14 years. Arm B was not inferior to Arm A: 5-year EFS was 77.5% and 71.6%, respectively (HR vs. Arm A: 0.74, 90% CI: 0.49-1.14). GRs were 54.9% in Arm A and 62.5% in Arm B. Hematological, gastrointestinal, and cardiovascular Grade ≥3 toxicities had higher frequencies in Arm B.

Conclusions: Intensive induction therapy showed non-inferiority in 5-year EFS when compared with the standard induction therapy. Higher toxicity was reported in Arm B with similar outcome, counterbalanced in GRs with a shorter treatment plan.

Clinicaltrials: gov Identifier: NCT02063022.