Can Proton Linear Accelerator Beams and Minibeams Achieve Superior Plan Quality Over Cyclotron-Generated Proton Beams and Photons in the Treatment of Lung Tumors?
T Gray1*, C Liu1, A Kolano2,3, J Donaghue4, J Farr2,3, K Stephans1, G Videtic1, 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-180 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To compare plan quality and robustness among photon Volumetric-modulated 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 lung tumors.
Methods: Twenty-two lesions from a total of twenty lung cancer patients were planned using CPBs and compared against LPBs, LPMBs and VMAT. All proton plans were optimized with multi-field optimization using the Monte Carlo. Benchmarked on photon plans, dose coverage to each lesion for proton plans was set to 98% of the ITV receiving the prescription (Rx) dose. Conformity index (CI), gradient index (GI), homogeneity index (HI), R50, V20Gy and mean dose of the lung were compared. Setup uncertainties of ±5 mm and ±3.5% range uncertainty were included in the robust evaluation, using V100%Rx > 99% of the GTV and V100%Rx >98% of the ITV.
Results: When compared to CPB plans, CI and R50 were significantly better for the LPB, and LPMB plans with a mean CI of 1.07 ± 0.21, 1.04 ± 0.24, and 1.03 ± 0.19 and a mean HI of 1.14 ± 0.05, 1.14 ± 0.04 and 1.12 ± 0.03, respectively (p<0.05). In comparison, mean CI and HI from photon VMAT plans were 1.15 ± 0.21, and 1.29 ± 0.09, respectively. R50, V20Gy to lung and mean lung dose all improved for all proton plans. When evaluated for V100%Rx of the ITV > 98% and for V100%Rx > 99% for the GTV, the lowest worst-case scenario showed ITV coverage of 97.43 ± 7.33% and 92.18 ± 16.48% for LMPB, respectively.
Conclusion: We successfully quantified plan quality and evaluated robustness for CPBs, LPBs and LPMBs for lung tumors. The LPB and LPMB stand as an excellent alternative to CPB therapy and can significantly decrease dose the 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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