The Impact of Radiotherapy in Children and Adolescents with Metastatic Rhabdomyosarcoma.

Abstract

PURPOSE\nThere is limited evidence to define the role of radiotherapy in children with metastatic rhabdomyosarcoma (mRMS). In the international XXXX study, children with mRMS or non-RMS soft tissue sarcoma were randomized to receive standard chemotherapy with/without bevacizumab, with radiotherapy recommended to all disease sites after chemotherapy cycle 6. We retrospectively evaluated the impact of radiotherapy on survival in the mRMS cohort.\n\n\nMETHODS AND MATERIALS\nPatients were grouped according to the radiotherapy they received: radical, partial or none. Radical irradiation was defined as radiotherapy delivered to all disease sites, unless a site was completely surgically resected. Partial irradiation was defined as radiotherapy to ≥1, but not all, disease sites. Landmark analysis excluded patients with an event prior to Day 221. Overall survival (OS) and event-free survival (EFS) were modelled using Cox proportional hazards models.\n\n\nRESULTS\nOf 102 patients with mRMS, 97 were included in the analysis for OS and 85 for EFS. Overall, 27 patients received radical irradiation, 46 partial irradiation and 24 no irradiation. EFS was not significantly different between patient groups after adjustment for prognostic factors (hazard ratio [HR]\u202f=\u202f0.520; P\u202f=\u202f0.054 for any vs no irradiation). Radiotherapy was associated with improved OS compared with no radiotherapy (adjusted HR\u202f=\u202f0.249; P\u202f=\u202f0.00025), with OS greater for radical versus partial irradiation (HR\u202f=\u202f0.245; P\u202f=\u202f0.039). The 3-year OS rate was 84%, 54% and 23% for patients receiving radical, partial and no irradiation, respectively. Radical treatment (surgery, irradiation or both) of the primary site improved EFS and OS compared with no treatment.\n\n\nCONCLUSIONS\nThese findings demonstrate variability in the application of radiotherapy for mRMS and support the routine use of radical treatment to the primary site. Radical irradiation to metastatic sites may further improve OS. The burden of such treatment should be balanced against prognosis; further studies are needed.