Gray Tara, Liu Chieh-Wen, Kolano Anna Maria, Donaghue Jeremy, Stephans Kevin, Videtic Gregory, Xia Ping, Farr Jonathan
Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, USA.
Department of Applications of Detectors and Accelerators to Medicine (ADAM) SA, Meyrin, Switzerland; Advanced Oncotherapy (AVO) plc, London, UK.
Med Dosim. 2025;50(3):209-215. doi: 10.1016/j.meddos.2025.01.006. Epub 2025 Feb 13.
To compare proton plans (IMPT) to VMAT plans and intercompare proton plans using 3 different spot sizes with robustness: cyclotron-generated proton beams (CPB) (σ: 2.7-7.0 mm), linear accelerator proton beams (LPB) (σ: 2.9-5.5 mm), and linear accelerator proton mini beams (LPMB) (σ: 0.9-3.9 mm) for the treatment of early-stage lung cancer. Twenty-two lesions from a total of twenty patients with early-stage lung cancer, originally treated with SBRT, were replanned using CPBs, LPBs, LPMBs, and VMAT using the same treatment planning system and dose calculation algorithm. The average intensity projected CTs (AIP-CT) were used for planning and 3D robust optimization was used for all proton plans. Conformity index (CI), homogeneity index (HI), R, lung V , and mean lung dose were compared among all proton plan types and with VMAT plans. Set-up uncertainties of ±5 mm and ±3.5% range uncertainty were included in the IMPT robust optimization and evaluation, using V > 98% of the ITV. The Wilcoxon signed-rank test was used to evaluate statistical differences between VMAT plans and all proton plan types. When compared to VMAT plans, all proton plans generally show improvement in CI, HI, Lung V , Mean lung dose, and R. The LPMB plans showed the most improvement from VMAT plans. Comparison between CPB and linear accelerator proton plans showed statistical significance (p < 0.05). R and mean lung dose for the CPB, LPB and LPMB plans were 3.6 ± 0.9, 3.1 ± 0.8 and 2.6 ± 0.6; 2.2 ± 1.1 Gy, 1.9 ± 1 Gy and 1.6 ± 0.9 Gy, respectively (p < 0.05). The mean R and mean lung dose from the VMAT plans were 4.1 ± 0.4 and 3.8 ± 2 Gy, respectively. The V (%) of lung and mean lung dose were improved across all proton plans when compared with those of VMAT plans. When evaluated for robustness in the worst-case scenario at V of the ITV > 98%, average ITV coverage of 98.6 ± 0.3%, 98.6 ± 0.6%, and 98.9 ± 0.6% were achieved for CPB plans, LPB plans, and LPMB plans, respectively. With decreased spot size, the LPB and LPMB plans are excellent alternatives to VMAT and cyclotron-generated proton plans with reduced dose to normal tissue and improved plan quality for early-stage lung cancer treatments.
比较质子计划（调强质子治疗，IMPT）与容积调强弧形放疗（VMAT）计划，并使用3种不同光斑尺寸对质子计划进行相互比较，同时考量稳健性：回旋加速器产生的质子束（CPB）（σ：2.7 - 7.0毫米）、直线加速器质子束（LPB）（σ：2.9 - 5.5毫米）以及直线加速器质子微束（LPMB）（σ：0.9 - 3.9毫米）用于早期肺癌的治疗。对20例接受过立体定向体部放疗（SBRT）的早期肺癌患者的22个病灶，使用相同的治疗计划系统和剂量计算算法，分别采用CPB、LPB、LPMB和VMAT进行重新计划。使用平均强度投影CT（AIP - CT）进行计划制定，所有质子计划均采用三维稳健优化。比较所有质子计划类型以及与VMAT计划之间的适形指数（CI）、均匀性指数（HI）、R、肺V值以及平均肺剂量。在IMPT稳健优化和评估中纳入±5毫米的摆位不确定性和±3.5%的范围不确定性，使用靶区内体积（ITV）的V > 98%。采用Wilcoxon符号秩检验评估VMAT计划与所有质子计划类型之间的统计学差异。与VMAT计划相比，所有质子计划在CI、HI、肺V值、平均肺剂量和R方面总体均有改善。LPMB计划相较于VMAT计划改善最为明显。CPB与直线加速器质子计划之间的比较具有统计学意义（p < 0.05）。CPB、LPB和LPMB计划的R和平均肺剂量分别为3.6 ± 0.9、3.1 ± 0.8和2.6 ± 0.6；2.2 ± 1.1 Gy、1.9 ± 1 Gy和1.6 ± 0.9 Gy（p < 0.05）。VMAT计划的平均R和平均肺剂量分别为4.1 ± 0.4和3.8 ± 2 Gy。与VMAT计划相比，所有质子计划的肺V（%）和平均肺剂量均有所改善。当在ITV的V > 98%的最坏情况下评估稳健性时，CPB计划、LPB计划和LPMB计划的平均ITV覆盖率分别达到98.6 ± 0.3%、98.6 ± 0.6%和98.9 ± 0.6%。随着光斑尺寸减小，LPB和LPMB计划是VMAT和回旋加速器产生的质子计划的优秀替代方案，可减少对正常组织的剂量并提高早期肺癌治疗的计划质量。
