{"title":"First Clinical Implementation of Step-and-Shoot Proton Arc Therapy for Head and Neck Cancer Treatment.","authors":"Peilin Liu, Xiaoda Cong, Jian Liang, Xiangkun Xu, Weili Zheng, Craig Stevens, Rohan Deraniyagala, Xiaoqiang Li, Xuanfeng Ding","doi":"10.1016/j.ijpt.2025.100749","DOIUrl":null,"url":null,"abstract":"<p><strong>Purpose: </strong>Dynamic Spot-scanning Proton Arc (SPArc<sub>-Dynamic</sub>) therapy has gained attention for enhancing dosimetric plan quality. However, its full clinical implementation remains under development. As an interim milestone, we developed step-and-shoot arc therapy (SPArc<sub>-step&shoot</sub>) for head-neck cancer treatment.</p><p><strong>Patients and methods: </strong>An in-house spot and energy-layer sparsity optimization algorithm was integrated into a clinical treatment planning system. The algorithm prioritized higher MU-weighted energy layers and spots to ensure delivery efficiency and superior plan quality while meeting machine requirements (≥0.02MU/spot). A Dynamic SPArc simulator calculated delivery times, and a machine-learning-based synthetic CT(synCT) platform monitored dose robustness. In June 2024, a head-neck cancer patient with parotid gland malignancy was treated using SPArc<sub>-step&shoot</sub> (6600 cGy[relative biological effectiveness] in 33 fx) with 9 static fields at 20-degree intervals. Comparative plans (SFO-IMPT, SPArc<sub>-Dynamic</sub>) were evaluated for dose metrics, delivery times, and adaptive planning.</p><p><strong>Results: </strong>SPArc<sub>-step&shoot</sub> and SPArc<sub>-Dynamic</sub> showed similar target coverage and organ-at-risks sparing, and the plan quality is superior to the 3-field SFO-IMPT in the brainstem, oral cavity, and spinal cord sparing. The simulated continuous arc delivery time is 15.9, 6.32, and 4.31 minutes for SPArc<sub>-step&shoot,</sub> SFO-IMPT, and SPArc<sub>-Dynamic</sub>, respectively. The actual recorded average treatment delivery time for SPArc<sub>-step&shoot</sub> in 33 fx is 16.7 ± 1.56 minutes. QA-CT and synCT showed a similar target coverage degradation and perturbation, and a replan was initiated.</p><p><strong>Conclusion: </strong>The SPArc<sub>-step&shoot</sub> therapy was successfully implemented in the clinical settings, and first patient was successfully treated between June and August 2024. The synCT platform serves a critical role in the daily monitoring process as SPArc<sub>-Dynamic</sub> might be more sensitive to the patient geometry changes in HNC treatment.</p>","PeriodicalId":36923,"journal":{"name":"International Journal of Particle Therapy","volume":"16 ","pages":"100749"},"PeriodicalIF":2.1000,"publicationDate":"2025-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12138570/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Particle Therapy","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1016/j.ijpt.2025.100749","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/6/1 0:00:00","PubModel":"eCollection","JCR":"Q3","JCRName":"ONCOLOGY","Score":null,"Total":0}
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Abstract
Purpose: Dynamic Spot-scanning Proton Arc (SPArc-Dynamic) therapy has gained attention for enhancing dosimetric plan quality. However, its full clinical implementation remains under development. As an interim milestone, we developed step-and-shoot arc therapy (SPArc-step&shoot) for head-neck cancer treatment.
Patients and methods: An in-house spot and energy-layer sparsity optimization algorithm was integrated into a clinical treatment planning system. The algorithm prioritized higher MU-weighted energy layers and spots to ensure delivery efficiency and superior plan quality while meeting machine requirements (≥0.02MU/spot). A Dynamic SPArc simulator calculated delivery times, and a machine-learning-based synthetic CT(synCT) platform monitored dose robustness. In June 2024, a head-neck cancer patient with parotid gland malignancy was treated using SPArc-step&shoot (6600 cGy[relative biological effectiveness] in 33 fx) with 9 static fields at 20-degree intervals. Comparative plans (SFO-IMPT, SPArc-Dynamic) were evaluated for dose metrics, delivery times, and adaptive planning.
Results: SPArc-step&shoot and SPArc-Dynamic showed similar target coverage and organ-at-risks sparing, and the plan quality is superior to the 3-field SFO-IMPT in the brainstem, oral cavity, and spinal cord sparing. The simulated continuous arc delivery time is 15.9, 6.32, and 4.31 minutes for SPArc-step&shoot, SFO-IMPT, and SPArc-Dynamic, respectively. The actual recorded average treatment delivery time for SPArc-step&shoot in 33 fx is 16.7 ± 1.56 minutes. QA-CT and synCT showed a similar target coverage degradation and perturbation, and a replan was initiated.
Conclusion: The SPArc-step&shoot therapy was successfully implemented in the clinical settings, and first patient was successfully treated between June and August 2024. The synCT platform serves a critical role in the daily monitoring process as SPArc-Dynamic might be more sensitive to the patient geometry changes in HNC treatment.
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