The impact of radiotherapy in metastatic rhabdomyosarcoma: Results from the XXXX study: Running title: Radiotherapy in metastatic rhabdomyosarcoma.

Radiation oncologists utilize radiation variably for children with metastatic rhabdomyosarcoma (RMS). Data from the XXXX study was retrospectively analyzed to validate the prior observation that the use of radiation is associated with improved outcomes, and guide future recommendations on radiation use in this patient group. The radiation delivered to 216 patients aged 0-21 years with metastatic RMS was retrospectively reviewed and classified as radical (all sites of disease irradiated within the protocol parameters), partial (some sites irradiated within the protocol parameters) and none (no radiation or delivered outside the protocol parameters). Landmark analysis excluded those with an event prior to day 221. Overall survival (OS) and progression free survival (PFS) were modelled using the Kaplan-Meier method to investigate the impact of radiation. The joint effect of treatment and known prognostic factors was examined using the Cox regression model. Overall 56 patients received radical, 104 partial and 56 no radiation per protocol. Due to non-randomised data, the groups were heterogeneous, particularly fewer sites of metatatic disease and less with bone metatases in those receiving radical radiation. 3-year PFS was 62.0% (95%CI 47.9-73.4) v 39.5% (29.8-49.1) v 30.1% (18.7-42.3)(p=0.002) for radical v partial v no radiotherapy respectively; 3-year OS was 70.1 % (55.8-80.6) v 53.1% (42.6-62.5) v 52.3% (38.3-64.5)(p=0.019) respectively. Multivariable analysis confirmed incremental improvement in OS with additional radiation with hazard ratio (HR) 1 v 1.8 v 2.4 (p=0.022) for radical v partial v no per protocol radiation. Radiation to all sites of disease seems to improve outcomes for children with metastatic RMS and should be considered when feasible. If not feasible, radiation is still recommended to the primary site and involved regional lymphadenopathy. Randomized clinical trials are required to confirm these findings, given the heterogeneity between the groups and potential confounding factors in this analysis.

Informations de copyright

Copyright © 2024. Published by Elsevier Inc.

Déclaration de conflit d'intérêts

Declaration of competing interest Julia Chisholm: lead investigator of relapse part of the investigator-led European paediatric Soft tissue Sarcoma study Group (EpSSG) Frontline and Relapse Rhabdomyosarcoma (FaR-RMS) study which has an arm supported financially by Bayer that will produce data for filing with the EMEA. No personal payment. Joint lead investigator for the FaR-RMS study which is funded by Cancer Research UK. No personal payment. Honoraria for teaching event paid by Bayer. JH Merks: Institutional fees paid for consulting with GSK, Merck and Bayer. Leadership: vice-chair Euro Ewing Consortium and Chair European Paediatric Soft tissue Sarcoma group. Mark Gaze: Financial support to attend meeting and give presentations from International Society of Paediatric Oncology (SIOP) to attend SIOP meeting in Ottawa 2023, European Federation of Medical Physicists (EFOMP) to attend EFOMP meeting in Athens 2023 and Romanian Society for Radiotherapy and Medical Oncology (RSRMO) to attend RSRMO meeting in Cluj Napoca 2023. Leadership: president Paediatric Radiation Oncology Society (PROS) since October 2023 (unremunerated) All other authors have no declared conflicts of interest.