Cyclophosphamide Compared With Ifosfamide in Consolidation Treatment of Standard-Risk Ewing Sarcoma: Results of the Randomized Noninferiority Euro-EWING99-R1 Trial

Purpose Relative efficacy and toxicity of cyclophosphamide compared with ifosfamide are debatable. The Euro-EWING99-R1 trial asked whether cyclophosphamide may replace ifosfamide in combination with vincristine and dactinomycin (vincristine, dactinomycin, and cyclophosphamide [VAC] v vincristine, dactinomycin, and ifosfamide [VAI]) after an intensive induction chemotherapy containing vincristine, ifosfamide, doxorubicin, and etoposide (VIDE) in standard-risk localized disease (NCT00020566). Methods Standard-risk Ewing sarcomas were localized tumors with either a good histologic response to chemotherapy (< 10% cells) or small tumors (< 200 mL) resected at diagnosis or receiving radiotherapy alone as local treatment. Patients entered the trial after six VIDE + 1 VAI courses. Allocated treatment was either 7 VAC courses with 1.5 g/m(2) of cyclophosphamide or seven VAI-courses with 6 g/m(2) ifosfamide. The limit of noninferiority was set at -8.5% for the 3-year event-free survival rate (EFS), equivalent to 1.43 in terms of the hazard ratio of event (HRevent). Results This large international trial recruited 856 patients between February 2000 and March 2010 (n = 431 receiving VAC and n = 425 receiving VAI). With a median follow-up of 5.9 years, the 3-year EFSs were 75.4% and 78.2%, respectively, the 3-year EFS difference was -2.8% (91.4% CI, -7.8 to 2.2%), the HRevent was 1.12 (91.4% CI, 0.89 to 1.41), and the HRdeath was 1.09 (91.4% CI, 0.84 to 1.42; intention-to-treat). The HRevent was 1.22 (91.4% CI, 0.96 to 1.54) on the per-protocol population. Major treatment modifications were significantly less frequent in the VAC arm (< 1%) than in the VAI arm (7%), mainly resulting from toxicity. Patients experienced more frequent thrombocytopenia in the VAC arm (45% v 35%) but fewer grade 2 to 4 acute tubular toxicities (16% v 31%). Conclusion Cyclophosphamide may be able to replace ifosfamide in consolidation treatment of standard-risk Ewing sarcoma. However, some uncertainty surrounding the noninferiority of VAC compared with VAI remains at this stage. The ongoing comparative evaluation of long-term renal and gonadal toxicity is crucial to decisions regarding future patients. (C) 2014 by American Society of Clinical Oncology