Proton-Photon Comparative Planning for Pediatric CNS Tumors: First Experiences of the Australian Bragg Centre for Proton Therapy and Research

Abstract

Objectives

To evaluate mean dose between focal proton beam therapy (PBT) and photon-based radiotherapy (XRT) using comparative planning in paediatric patients with central nervous system (CNS) tumours.

Methods

Between January 2022 and June 2023, 23 patients were referred to the Australian Bragg Centre for Proton Therapy and Research (ABCPTR) for comparative planning to be evaluated for consideration of focal PBT. Nineteen patients were from Australia and four from New Zealand. Eighteen patients proceeded with comparative planning based on locally defined target volumes and planning constraints. All calculated plans underwent prospective analysis of quality metrics, including target volume coverage, integral dose, and dose(s) to organs at risk (OAR).

Results

Comparable target volume metrics were achieved between PBT and XRT. PBT achieved a mean reduction in integral dose of 30.2% (range 15.0 – 54.0%) in all cases. Further, dose to most OAR favoured PBT. Notable areas of dose reduction to OARs were most commonly seen in the right optic nerve, right lens, right globe, left temporal lobe and left cochlea. Hippocampi were equally receiving lower mean doses when compared to XRT unless directly adjacent to the clinical and planning target volumes.

Conclusion

In this cohort, dosimetric advantages were identified using PBT when compared to XRT with respect to reduction in integral dose and OAR. This relative reduction in integral dose may translate into a reduced risk of second malignancies when compared with XRT and reduced mean doses to OAR have the potential to improve quality of survivorship. PBT should be considered the standard of care in Australian paediatric patients with CNS tumours requiring focal irradiation.