Departments of Radiation Oncology, The University of Texas M,D, Anderson Cancer Center, 1515 Holcombe Blvd,, Unit 1150, Houston, TX 77030, USA.
Radiat Oncol. 2013 Dec 17;8:289. doi: 10.1186/1748-717X-8-289.
For treatment of the entire cranium using passive scattering proton therapy (PSPT) compensators are often employed in order to reduce lens and cochlear exposure. We sought to assess the advantages and consequences of utilizing compensators for the treatment of the whole brain as a component of craniospinal radiation (CSI) with PSPT. Moreover, we evaluated the potential benefits of spot scanning beam delivery in comparison to PSPT.
Planning computed tomography scans for 50 consecutive CSI patients were utilized to generate passive scattering proton therapy treatment plans with and without Lucite compensators (PSW and PSWO respectively). A subset of 10 patients was randomly chosen to generate scanning beam treatment plans for comparison. All plans were generated using an Eclipse treatment planning system and were prescribed to a dose of 36 Gy(RBE), delivered in 20 fractions, to the whole brain PTV. Plans were normalized to ensure equal whole brain target coverage. Dosimetric data was compiled and statistical analyses performed using a two-tailed Student's t-test with Bonferroni corrections to account for multiple comparisons.
Whole brain target coverage was comparable between all methods. However, cribriform plate coverage was superior in PSWO plans in comparison to PSW (V95%; 92.9 ± 14 vs. 97.4 ± 5, p < 0.05). As predicted, PSWO plans had significantly higher lens exposure in comparison to PSW plans (max lens dose Gy(RBE): left; 24.8 ± 0.8 vs. 22.2 ± 0.7, p < 0.05, right; 25.2 ± 0.8 vs. 22.8 ± 0.7, p < 0.05). However, PSW plans demonstrated no significant cochlear sparing vs. PSWO (mean cochlea dose Gy(RBE): 36.4 ± 0.2 vs. 36.7 ± 0.1, p = NS). Moreover, dose homogeneity was inferior in PSW plans in comparison to PSWO plans as reflected by significant alterations in both whole brain and brainstem homogeneity index (HI) and inhomogeneity coefficient (IC). In comparison to both PSPT techniques, multi-field optimized intensity modulated (MFO-IMPT) spot scanning treatment plans displayed superior sparing of both lens and cochlea (max lens: 12.5 ± 0.6 and 12.9 ± 0.7 right and left respectively; mean cochlea 28.6 ± 0.5 and 27.4 ± 0.2), although heterogeneity within target volumes was comparable to PSW plans.
For PSPT treatments, the addition of a compensator imparts little clinical advantage. In contrast, the incorporation of spot scanning technology as a component of CSI treatments, offers additional normal tissue sparing which is likely of clinical significance.
为了降低晶状体和耳蜗的照射剂量，在使用被动散射质子治疗（PSPT）治疗整个头颅时，通常会使用补偿器。我们旨在评估在使用 PSPT 进行颅脊髓照射（CSI）时使用补偿器治疗全脑的优势和后果。此外，我们评估了与 PSPT 相比，点扫描束输送的潜在益处。
使用 50 例连续 CSI 患者的计划计算机断层扫描（CT）扫描，分别生成带有和不带有 Lucite 补偿器（PSW 和 PSWO）的被动散射质子治疗计划。随机选择 10 例患者作为扫描束治疗计划的亚组进行比较。所有计划均使用 Eclipse 治疗计划系统生成，并规定为全脑 PTV 提供 36 Gy（RBE）的剂量，分 20 次进行照射。计划归一化以确保全脑靶区覆盖相同。使用双尾学生 t 检验和 Bonferroni 校正进行统计学分析，以比较多组数据。
所有方法的全脑靶区覆盖情况相似。然而，与 PSW 计划相比，PSWO 计划的筛板覆盖更好（V95%；92.9±14 比 97.4±5，p<0.05）。如预期的那样，PSWO 计划的晶状体照射明显高于 PSW 计划（左：最大晶状体剂量 Gy（RBE）：24.8±0.8 比 22.2±0.7，p<0.05；右：25.2±0.8 比 22.8±0.7，p<0.05）。然而，PSW 计划与 PSWO 计划相比，耳蜗的保护没有明显差异（平均耳蜗剂量 Gy（RBE）：36.4±0.2 比 36.7±0.1，p=NS）。此外，与 PSWO 计划相比，PSW 计划的剂量均匀性较差，这反映在全脑和脑干均匀性指数（HI）和不均匀性系数（IC）方面的显著变化。与两种 PSPT 技术相比，多野优化强度调制（MFO-IMPT）点扫描治疗计划对晶状体和耳蜗的保护更优（最大晶状体：右和左分别为 12.5±0.6 和 12.9±0.7；平均耳蜗 28.6±0.5 和 27.4±0.2），尽管靶区的异质性与 PSW 计划相似。
对于 PSPT 治疗，添加补偿器几乎没有带来临床优势。相比之下，将点扫描技术作为 CSI 治疗的一部分，提供了额外的正常组织保护，这可能具有临床意义。
