BOSTON -- Proton radiotherapy (PRT) is safe and effective in children and young adults with neuroblastoma, according to research presented at the American Society for Radiation Oncology (ASTRO) annual meeting. 

A team from Mass General Brigham in Boston prospectively evaluated PRT's toxicity and survival outcomes in this population in a phase II trial involving 28 participants, with findings suggesting the modality's advantages over standard radiation therapy translate into meaningful clinical benefit, noted lead author Palak Patel, MD, and colleagues. 

"In this prospective phase II study, PRT for neuroblastoma demonstrated favorable toxicity profiles and disease control rates," the researchers noted. 

Radiation therapy is a key treatment component for neuroblastoma but contributes to both acute and long-term toxicities, the authors noted. Conversely, PRT reduces low-dose radiation exposure to normal tissue and may mitigate that morbidity, they wrote, although prospective data on its toxicity and outcomes in young neuroblastoma patients remain limited. 

To address the gap, the researchers recruited patients aged six months to 25 years old with neuroblastoma who underwent PRT to the primary site following standard Children's Oncology Group (COG) target volume guidelines, with treatment to metastatic sites at at the discretion of the treating physicians in discussion with patients and families.  

Toxicities were graded using Common Terminology Criteria for Adverse Events (CTCAE) v4.0 and categorized as acute (occurring during RT or up to 90 days after the completion of RT and resolving within 6 months after completion of RT) or late (occurring > 90 days from the completion of RT or any acute toxicities that did not resolve within six months). Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan-Meier methods. Twenty-eight patients were enrolled, 27 with high-risk disease. 

According to the findings, acute grade ≥ 3 toxicities were primarily hematologic, including lymphopenia in 10 patients, neutropenia in eight, and leukopenia in 10. Late grade ≥ 3 toxicities were rare, occurring in four patients: lymphopenia in two, leukopenia in one, and hearing impairment in one. With a median follow-up of 3.7 years, one patient experienced combined local and distant recurrence and five developed distant-only relapse, based on a small sample. Three-year PFS and OS were 77.2% and 87.6%. 

"Radiation therapy is an important treatment modality for patients with neuroblastoma but contributes to acute and late toxicities," the authors wrote. "Proton RT reduces low dose radiation to normal tissue and may mitigate morbidity.” 

The results should inform both future trial design and survivorship care planning for this patient population, the researchers suggested. Longer follow-up in larger cohorts will be needed to fully characterize late toxicity burden and confirm durable disease control. 

"These findings support PRT as a strategy to reduce long-term morbidity without compromising oncologic outcomes,” the group concluded. 

Check out AuntMinnie's full coverage of ASTRO 2026 on our ShowCast.