Radiation Therapy to Sites of Metastatic Disease as Part of Consolidation in High-Risk Neuroblastoma: Can Long-term Control Be Achieved?

Casey, DL et al, 2018, International Journal of Radiation Oncology Biology Physics

Link to abstract

https://www.ncbi.nlm.nih.gov/pubmed/29439882

Introduction

Radiation therapy (RT) to metastatic sites as part of consolidative therapy in neuroblastoma is standard in Children’s Oncology Group protocols, but has not been rigorously studied.

Description

Retrospective review of 159 HR NB patients treated with RT that was directed to 244 metastatic sites at Memorial Sloan Kettering Cancer Center between years 2000-2015. 21 Gy BID (twice-a-day) was typically given.

Results Summary

The 5-year local control (LC) rate (of the irradiated metastatic site) was 81%. Sites that became negative on MIBG after induction chemotherapy had a higher LC rate as compared to those that were persistent after induction treatment (92% vs. 67%, respectively; statistically significant). Persistent disease after induction chemotherapy was the only significant prognostic factor for LC on multivariable analysis. Importantly, LC at irradiated metastatic sites was associated with an overall survival benefit.

Limitations

A majority (62%) of patients had one irradiated metastatic site. This study does not answer the question about whether aggressive irradiation of all metastatic sites in patients with numerous sites of metastatic neuroblastoma is helpful. The authors commented: “The maximum number of sites that can and should be irradiated as a part of consolidative therapy remains unknown.” 

This study could not tell us if persistent metastatic sites after chemotherapy should receive RT dose-escalation beyond 21 Gy. 

The radiation was delivered twice-a-day as part of the MSKCC standard; this is not typically done at other cancer centres due to the challenging logistics of BID radiation treatment.

Bottom Line

This retrospective study demonstrates that local control of metastatic sites in patients with neuroblastoma is important and associated with a survival benefit. Patients with metastatic sites that resolve after initial chemotherapy should be considered for RT to ensure local control.

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