Patients with high-risk neuroblastoma (HR-NBL) require radiation to the primary tumor site and sites of persistent metastatic disease. Proton radiotherapy (PRT) may promote organ sparing, but long-term outcomes have not been studied.
Sequential patients with HR-NBL received PRT: 2160 cGy(RBE) to primary tumor bed and persistent metastatic sites, with 3600 cGy(RBE) to gross residual disease.
From 9/2010-9/2015, 45 patients with HR-NBL received PRT following systemic therapy, primary tumor resection, and high-dose chemotherapy with stem cell rescue. Median age was 46 months at the time of PRT (range 10m – 12y); 23 (51%) were boys. Primary tumors were adrenal in 40 (89%); 11 (24%) received boost. Ten metastatic sites in 8 patients were radiated. Double scattered (DS) proton beams were used for 19 (42%) patients, in combination with x-rays for 2 (5%). The remaining 26 (58%) received pencil beam scanning (PBS), available since 1/2013. We observed 97% freedom from primary site recurrence at 3, 4 and 5 years. Overall survival rates were 89%, 80%, 80% and disease-free survival rates were 77%, 70%, and 70%, at 3, 4, and 5 years, respectively. With median follow-up of 48.7 months from diagnosis (range 11 – 90 months) for all patients (57.4 months for those alive), 37 (82%) patients are alive, and 32 (71%) are without evidence of disease. One patient experienced locoregional recurrence; the remaining 12 (27%) experienced relapse at distant, non-radiated sites. Acute toxicities during treatment were mainly grade 1. No patient has experienced WHO G3/4 long-term renal or hepatic toxicity. PBS plans required less planning time and resources than DS plans.
We observe excellent outcomes in patients treated with PRT for HR-NBL from 2010-2015, with 82% of patients alive and 97% free of primary site recurrence. No patient has experienced long-term renal or liver toxicity. This treatment maximizes normal tissue preservation and is appropriate for this patient population.