The team from the Department of Pediatric Oncology, National Cancer Center Japan, Tokyo, Japan.
and the Cancer Medicine, Cooperative Graduate School, The Jikei University Graduate School of Medicine, Tokyo, Japan have just published an article in Pediatric Blood and Cancer about a metronomic maitenance in RMS.

The authors Risa Yanai, Minako Sugiyama, Bunpei Miyazaki, Natsumi Kikuchi, Kosuke Tamefusa, Kayoko Tao, Eriko Uchida, Kiyotaka Isobe, Kan Yonemori, Ayumu Arakawa thus confirm the activity of the metronomicregimen in 18 relapsing and refractory RMS. Interstingly, they suggest starting at 80% of the dose.

Abstract

Background

: Relapsed or refractory rhabdomyosarcoma (RMS) has a poor prognosis, and optimal treatment remains an unmet need. Vinorelbine (VNR) and low-dose metronomic cyclophosphamide (CPM) have shown clinical efficacy and are used as maintenance therapy in localized and metastatic disease; however, dose reductions are frequently required due to myelosuppression. This study evaluated the safety, efficacy, and optimal dosing of VNR and CPM in pediatric patients with relapsed or refractory RMS.

Methods: Pediatric patients treated with VNR and CPM at our institution between March 2014 and May 2024 were retrospectively reviewed. Dosing was based on the RMS 2005 protocol, with dose reductions implemented before or during treatment to minimize treatment interruptions.

Results: Eighteen patients received 139 cycles of therapy (median age at initiation, 15.6 years; range, 7-21 years), including 13 relapsed and 5 refractory cases. The median number of cycles administered was 5.5 (range, 1-26), with a median interval of 28 days. The median adjusted dose ratios over three cycles were 55% for VNR and 53.5% for CPM. Disease control lasting longer than 10 months was achieved in six patients (33%). Neutropenia occurred in 89% of patients, whereas anemia and thrombocytopenia requiring transfusion occurred in 28% and 22%, respectively. No grade 4 non-hematologic toxicities or treatment-related deaths were observed after dose adjustment.

Conclusions: VNR and continuous low-dose CPM chemotherapy were safe and feasible with dose adjustments. In heavily pretreated patients, initiating therapy at approximately 80% of the standard dose may be appropriate.