Can Proton Linear Accelerator Beams and Minibeams Achieve Superior Plan Quality Over Cyclotron-Generated Proton Beams and Photons in the Treatment of Head and Neck Tumors?
T Gray1*, S Ahmed1, C Liu1, A Kolano2,3, J Donaghue4, J Farr2,3, J Suh1, P Xia1, (1)Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH (2)Applications Of Detectors And Accelerators To Medicine (ADAM) SA, Meyrin, Switzerland (3)Advanced Oncotherapy plc, London, UK (4) Cleveland Clinic Fairview, Rocky River, OH
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PO-GePV-T-181 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To compare plan quality and robustness among photon Volumetric Arc Therapy (VMAT), Intensity-Modulated Proton Therapy using cyclotron-generated proton beams (CPB), linear accelerator proton beams (LPB), and linear accelerator proton minibeams (LPMB) for the treatment of head and neck cancers.
Methods: Ten head and neck cancer patients were planned using CPBs and compared against LPBs, LPMBs and VMAT. All proton plans were optimized with multi-field optimization technique using the Monte Carlo algorithm. Benchmarked on the photon plans, the dose to each lesion in proton plans was also normalized such that the 95% of the PTV receives the prescription dose. Conformity index (CI), homogeneity index (HI), mean body dose and dose to critical OARs were compared. Setup uncertainties of ±3 mm and ±3.5% range uncertainties were included in robust evaluation using V100%Rx > 95% of the CTV for proton plans. Dose metrics to OARs were also evaluated and compared among all plan types.
Results: When compared to CPB plans, CI and HI were significantly better (p<0.05) for the LPB, and LPMB plans when compared with VMAT plans. Up to a 38% decrease in the dose metrics to OARs was seen for all proton plans when compared to VMAT plans. The mean body dose decreased up to 32% for all proton plans when compared with VMAT plans. The robust evaluation shows the most significant improvement for the LMPB plans, with an average of 90.87% coverage of the CTV across all worst-case scenarios.
Conclusion: We successfully evaluated and quantified plan quality and robustness for CPBs, LPBs and LPMBs for head and neck tumors. The LPB and LPMB stand as an excellent alternative to VMAT and CPB therapy and can significantly decrease dose to normal tissue.
Funding Support, Disclosures, and Conflict of Interest: Jonathan Farr holds a senior management position at ADAM SA, Meyrin, Switzerland and is a shareholder in Advanced Oncotherapy (AVO), plc, London, UK. Anna-Maria Kolano is an employee of ADAM SA and participates in the employee share option program of AVO. Ping Xia receives research funding support from AVO.
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