Implications of Image-Defined Risk Factors and Primary-Site Response on Local Control and Radiation Treatment Delivery in the Management of High-Risk Neuroblastoma: Is There a Role for De-escalation of Adjuvant Primary-Site Radiation Therapy?

PURPOSE: The predictive value of Image-Defined Risk Factors (IDRFs) developed by the International Neuroblastoma Risk Group Task Force as it relates to primary-site management is undefined and may aid patient selection for de-escalation of adjuvant radiation therapy to the primary site in high-risk neuroblastoma. METHODS AND MATERIALS: Patients (N = 76) with high-risk neuroblastoma treated on prospective trials at our institution from 1997 to 2014 were eligible for inclusion. IDRFs were defined based on pretherapy imaging. Overall survival, progression-free survival, and locoregional failure-free survival (LRFFS) were described using the Kaplan-Meier estimator and tested across strata by using the log-rank test.
RESULTS: Twenty of 76 patients (26%) experienced local (n = 6), regional (n = 6), or combined locoregional failure (n = 8) with or without distant failure. Ten (50%) of the locoregional failures had concurrent distant relapse. Of patients who completed all therapy, both those with no IDRFs and those with >90% resection had a 3-year LRFFS of 100%, with or without radiation therapy. Patients with either ≥1 IDRF or <Gross Total Resection (GTR) or the inability to complete all therapy had inferior 3-year LRFFS of 77.8% and 14.4% with or without radiation therapy, respectively (P < .04). Patients treated with a dose ≥30.6 Gy as part of therapy for residual disease had an 83.3% locoregional control rate.
CONCLUSIONS: Patients with >90% tumor resection and no primary site IDRFs at diagnosis may be candidates for de-escalation of adjuvant primary-site radiation therapy, although validation of these findings in future studies is required.