Proton Arc Therapy For Head-and-Neck Cancer: Comparison With and Impact on Proton Range Uncertainty Reduction Benefits

Document Type

Conference Proceeding

Publication Date

6-2024

Publication Title

International Journal of Particle Therapy

Abstract

Background and aims: Proton therapy allows for a more conformal dose distribution to the tumor than conventional photon treatments. However, uncertainties in the in vivo proton range remain considerable. Benefits of range uncertainty reductions depend on clinical practices. Current intensity-modulated proton therapy (IMPT) treatments rely on target irradiation from a few different directions, but proton arc therapy (PAT), for which the tumor is irradiated from dozens of angles, is under investigation. It is therefore necessary to investigate how the clinical implementation of PAT may compare to and affect benefits of proton range uncertainty reductions. Methods: For 20 head-and-neck cancer patients, four different proton therapy treatment plans were created: an IMPT and a PAT treatment plan which assume current clinical range uncertainties of ~3.5% (IMPT3.5% and PAT3.5%), and corresponding treatment plans assuming that range uncertainties can be reduced to 1% (IMPT1% and PAT1%). Plan evaluation included target and organ-at-risk (OAR) doses and normal tissue complication probabilities (NTCPs) for the patient experiencing grade 4 xerostomia or grade ≥ 2 larynx edema due to the dose delivered to the parotid glands and larynx, respectively. Results: Mean NTCP reductions resulting from PAT implementation (IMPT3.5%- PAT3.5%) were 3.2 percentage points (pp) and 4.2 pp in the nominal and worst-case scenario, respectively. Range uncertainty reduction benefits during IMPT (IMPT3.5%- IMPT1%) were 0.9 pp and 2.0 pp. After PAT implementation, range uncertainty reductions (PAT3.5%- PAT1%) were accompanied by mean NTCP reductions of 0.2 pp and 1.0 pp, but range uncertainty reduction benefits remained comparatively high in cases with bilateral tumors. Conclusions: The clinical benefit of PAT implementation was more than twice as high as the benefit of a 3.5% to 1% range uncertainty reduction during IMPT. Especially in cases with tumor locations allowing for more complete leveraging of the considerably higher number of beam angles during PAT, range uncertainty reductions are expected to remain beneficial even if achieved subsequently to clinical implementation of PAT. Acknowledgements: ST is the recipient of a Mitacs Accelerate Fellowship. TRIUMF receives funding from the National Research Council of Canada. PL and XD’s efforts are partially supported by IBA industrial research funding

Volume

12

Issue

Suppl

First Page

2

Comments

62nd Annual Conference of the Particle Therapy Cooperative Group (PTCOG), June 10-15, 2024, Singagpore

DOI

10.1016/j.ijpt.2024.100116

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