Background
Secondary analysis of RT outcomes from CCG 3891. Evaluated the role, dose, and volume of local RT in high-risk neuroblastoma patients enrolled on CCG 3891. Assessed local failure rates and relationship between RT delivery and outcomes in the context of myeloablative consolidation.
Interventions and follow up
Arm A: Involved-field RT to primary site post-consolidation (median dose 20 Gy; range 15–30 Gy)
Primary endpoint: Local failure, local PFS
mFollow up: 5.0 year
Primary endpoint: Local failure, local PFS
mFollow up: 5.0 year
Results
Arm B (comparison group): Patients who did not receive RT or received non-standard RT (protocol deviations)
Local failure (no RT): Significantly higher vs RT-treated patients
Local control at 2 yr (RT delivered): ~80%
Dose-response: Doses <15 Gy associated with higher local failure rates
Local failure (no RT): Significantly higher vs RT-treated patients
Local control at 2 yr (RT delivered): ~80%
Dose-response: Doses <15 Gy associated with higher local failure rates
Adverse events
Main adverse events: Abdominal RT: hepatotoxicity especially with TBI; renal dose-volume concerns; scoliosis risk with vertebral body inclusion. Hepatic veno-occlusive disease risk when RT follows TBI in HDCT.
Conclusions
Local RT to the primary site is an important component of neuroblastoma therapy — omission results in higher local failure rates. Doses around 21.6 Gy became the standard based on this and subsequent analyses balancing efficacy and toxicity.
Key Limitations
Key Limitations: Secondary/retrospective analysis; not a prospective RT randomization. RT delivery varied substantially across institutions. TBI used in consolidation confounds local RT dose-response. RT volumes were not standardized.
Clinical Context
This analysis contributed to standardization of local RT dose at 21.6 Gy for neuroblastoma primary site in subsequent COG trials. The transition from TBI-based to chemotherapy-only HDCT (CEM) changed the hepatotoxicity profile of abdominal RT. IMRT with kidney/liver sparing is now standard technique.
References