Francis H. Burr Proton Therapy Center, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.
Int J Radiat Oncol Biol Phys. 2013 Sep 1;87(1):188-94. doi: 10.1016/j.ijrobp.2013.04.048.
To describe, in a setting of non-small cell lung cancer (NSCLC), the theoretical dosimetric advantages of proton arc stereotactic body radiation therapy (SBRT) in which the beam penumbra of a rotating beam is used to reduce the impact of range uncertainties.
Thirteen patients with early-stage NSCLC treated with proton SBRT underwent repeat planning with photon volumetric modulated arc therapy (Photon-VMAT) and an in-house-developed arc planning approach for both proton passive scattering (Passive-Arc) and intensity modulated proton therapy (IMPT-Arc). An arc was mimicked with a series of beams placed at 10° increments. Tumor and organ at risk doses were compared in the context of high- and low-dose regions, represented by volumes receiving >50% and <50% of the prescription dose, respectively.
In the high-dose region, conformality index values are 2.56, 1.91, 1.31, and 1.74, and homogeneity index values are 1.29, 1.22, 1.52, and 1.18, respectively, for 3 proton passive scattered beams, Passive-Arc, IMPT-Arc, and Photon-VMAT. Therefore, proton arc leads to a 30% reduction in the 95% isodose line volume to 3-beam proton plan, sparing surrounding organs, such as lung and chest wall. For chest wall, V30 is reduced from 21 cm(3) (3 proton beams) to 11.5 cm(3), 12.9 cm(3), and 8.63 cm(3) (P=.005) for Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively. In the low-dose region, the mean lung dose and V20 of the ipsilateral lung are 5.01 Gy(relative biological effectiveness [RBE]), 4.38 Gy(RBE), 4.91 Gy(RBE), and 5.99 Gy(RBE) and 9.5%, 7.5%, 9.0%, and 10.0%, respectively, for 3-beam, Passive-Arc, IMPT-Arc, and Photon-VMAT, respectively.
Stereotactic body radiation therapy with proton arc and Photon-VMAT generate significantly more conformal high-dose volumes than standard proton SBRT, without loss of coverage of the tumor and with significant sparing of nearby organs, such as chest wall. In addition, both proton arc approaches spare the healthy lung from low-dose radiation relative to photon VMAT. Our data suggest that IMPT-Arc should be developed for clinical use.
在非小细胞肺癌（NSCLC）环境中描述质子弧形立体定向体放射治疗（SBRT）的理论剂量学优势，其中旋转束的射束半影用于减少射程不确定性的影响。
13 名接受质子 SBRT 治疗的早期 NSCLC 患者接受了光子容积调强弧形放射治疗（Photon-VMAT）和内部开发的质子被动散射（Passive-Arc）和强度调制质子治疗（IMPT-Arc）的弧形计划方法的重复计划。通过在 10°增量处放置一系列光束来模拟弧形。在高剂量区和低剂量区，比较肿瘤和危及器官的剂量，分别代表分别接受处方剂量> 50％和<50％的体积。
在高剂量区，适形性指数值分别为 2.56、1.91、1.31 和 1.74，均匀性指数值分别为 1.29、1.22、1.52 和 1.18，适用于 3 个质子被动散射束、Passive-Arc、IMPT-Arc 和 Photon-VMAT。因此，质子弧形可将 95％等剂量线体积减少 30％至 3 束质子计划，从而保护周围器官，如肺和胸壁。对于胸壁，V30 从 21 cm3（3 束质子）分别减少到 Passive-Arc、IMPT-Arc 和 Photon-VMAT 的 11.5 cm3、12.9 cm3 和 8.63 cm3（P = 0.005）。在低剂量区，同侧肺的平均肺剂量和 V20 分别为 5.01 Gy（相对生物效应[RBE]）、4.38 Gy（RBE）、4.91 Gy（RBE）和 5.99 Gy（RBE）和 9.5％、7.5％、9.0％和 10.0％，适用于 3 束、Passive-Arc、IMPT-Arc 和 Photon-VMAT。
与标准质子 SBRT 相比，质子弧形立体定向体放射治疗和 Photon-VMAT 可产生更符合形状的高剂量体积，而不会丢失肿瘤的覆盖范围，并显著保护附近的器官，如胸壁。此外，与光子 VMAT 相比，两种质子弧形方法都可以使健康肺免受低剂量辐射的影响。我们的数据表明，应开发 IMPT-Arc 用于临床应用。
