Radiation therapy to metastatic sites among patients with high-risk neuroblastoma in first-line therapy

Relevance. Radiation therapy (RT) is one of the components of multimodal treatment among patients with high-risk neuroblastoma (NB), and in combination with surgical treatment is a mandatory element of local control of the primary tumor. At the same time, RT for metastatic sites persisting after completion of induction therapy is not a standard protocol treatment in primary patients with high-risk NB. The effect of RT on metastatic sites on improving long-term survival and reducing recurrence rates continues to be studied. Aim to the study – to investigate approaches to RT for single metastatic foci persisting after induction therapy among patients with NB highrisk group as part of the consolidation phase of first-line therapy. Materials and methods. The retrospective analysis included 11 patients with high-risk NB who underwent RT for metastatic foci as part of first-line therapy at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology, Ministry of Health of Russia from 01.2012 to 12.2023. Patients received therapy according to the modified protocol GPON-NB2004. The indication for RT was the persistence of a single metastatic site detected by 123I-metaiodobenzylguanidine scintigraphy or computed tomography/magnetic resonance imaging after completion of induction chemotherapy. Results. The median age was 31.9 months (range 9.4–128.6 months). All patients were initially with stage 4 disease (one patient had metastatic focus in the orbit without detection of the primary tumor). MYCN gene amplification was detected in 4/11 (36 %) cases. 10/11 (91 %) patients achieved а partial response after induction therapy. In all cases, only one metastatic focus was irradiated. 2/11 patients received radiation to both the primary tumor and metastatic focus. 10/11 patients received RT to metastatic sites localized in skeletal bones, 1/11 – to a distant lymph node. Seven of 11 sites received 21 Gy in 14 fractions. The median follow-up was 40 months (range 13–97 months). Only 1 of 11 patients receiving metastatic site irradiation experienced relapse in an irradiated distant site 24 months later. The 3-year relapse-free survival and overall survival were 54 % and 80 % respectively. Conclusions. RT may be an effective method of local control in oligometastatic disease and in case of persisted single metastatic foci after induction chemotherapy in the treatment of high-risk NB. Additional large studies are needed to confirm the role of RT in improving survival with irradiation of metastatic sites.