Vinorelbine and Low-Dose Cyclophosphamide As Maintenance Therapy in the Treatment of Ewing Sarcoma Rationale for the International INTER-EWING-1 Trial for Ewing Sarcoma Patients

INTRODUCTION:Ewing sarcoma (ES) is a malignant bone tumor with high relapse rates, especially in multi-metastatic disease despite multimodal treatment. The role of maintenance therapy in ES remains undefined. We systematically reviewed clinical trial data to assess the feasibility and rationale for maintenance therapy in localized and metastatic disease, with the aim to help selecting drugs to introduce as maintenance therapy within the trial. METHODS:A PubMed search identified studies evaluating maintenance or metronomic therapy in ES and other pediatric sarcomas published between January 1990 and January 2020. Inclusion of articles required clinical use of maintenance therapy in pediatric (Ewing) sarcoma; case reports, preclinical studies, reviews, and phase I trials were excluded. A second PubMed search (February 2020-June 2025) updated the evidence base. Data on study design, patient characteristics, treatment regimens, and outcomes were extracted. RESULTS:Of 3040 records identified in the first search, 20 were included: 11 included ES patients, 9 in other pediatric sarcomas. The update yielded 9 additional studies (3 ES, 6 other sarcomas). Vinorelbine, alone or combined with low-dose cyclophosphamide, was most frequently investigated, mainly in heavily pretreated relapsed or refractory ES patients, showing modest clinical activity. Strongest evidence derived from rhabdomyosarcoma (RMS) patients, where the randomized EpSSG RMS 2005-trial demonstrated improved long-term survival with vinorelbine/cyclophosphamide maintenance. CONCLUSION:Vinorelbine plus low-dose cyclophosphamide represent a rational backbone for ES maintenance therapy, supported by evidence in RMS and limited ES data. Ongoing international efforts will define their clinical role when given for 6 months. Future studies should eventually clarify optimal duration, alternative agents, and long-term safety.