Local Control With Reduced-Dose Radiation Therapy for High-Risk Neuroblastoma: Results From a Prospective Clinical Trial.

Abstract

Little is known about local control, toxicity, and survival outcomes associated with reduced-dose radiation therapy (RT) for high-risk neuroblastoma (HR-NB). In this prospective pilot study, eligible patients had HR-NB with a gross total resection (no tumor evident on postsurgery CT or MRI) of the primary site after induction systemic therapy. Patients were treated with 15 or 18 Gy to the primary site in 1.5 Gy fractions delivered twice daily. The primary outcome was to assess local failure (LF) at the primary site. The secondary outcomes included overall survival (OS), event-free survival (EFS), distant-metastasis-free survival (DMFS), and acute toxicity from RT. A total of 78 patients were enrolled between 2014 and 2023 at a single institution. Median follow-up from time of RT was 35 months (interquartile range [IQR] 19-67 months). Median age at the time of RT was 3.8 years (IQR, 2.4-5.6). Forty-seven patients (60%) received proton RT, 53 (68%) received 15 Gy, and 25 (32%) received 18 Gy. Three patients experienced LF at the primary site, all at 15 Gy. At 1 and 5 years post-RT, the rate of LF was 2.6 and 3.9%, respectively. There was no significant difference in the risk of LF by MYCN-amplification status (P = .5). There was no significant difference in OS, EFS, or DMFS between the 15 Gy and 18 Gy cohorts (P = .95, P = .45, and P = .45, respectively). Thirty-two patients (41%) experienced acute toxicity, which included grade 1 to 2 fatigue, nausea, and decreased appetite. For patients with HR-NB who have a GTR of the primary site, reduced-dose RT of 15 to 18 Gy is associated with an approximately 96% local control rate with negligible acute toxicity.