Center for Proton Therapy, Paul Scherrer Institute, ETH Domain, Villigen, Switzerland.
Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma - Università Cattolica del Sacro Cuore, Rome, Italy.
Radiother Oncol. 2020 Aug;149:197-204. doi: 10.1016/j.radonc.2020.04.052. Epub 2020 May 5.
This study analyses the dosimetric and dose averaged Linear Energy transfer (LETd) correlation in paediatric craniopharyngioma (CP) patients with and without radiation-induced cerebral vasculopathies (RICVs) treated with pencil beam scanning (PBS) proton therapy (PT).
We reviewed a series of 16 CP patients treated with PT to a median dose of 54 Gy(RBE). Two (12.5%) index patients presented RICVs 14 and 24 months (median, 19) after PT. Organs at risks (OARs) as bilateral internal carotid arteries (ICAs) and circle of Willis were contoured based on CTs and MRIs pre- and post-PT. Dosimetry was reviewed and LETd distributions were calculated; LETd metric for PTVs and OARs were analysed. For a sub-cohort, dosimetric and LETd values robustness due to range uncertainties were computed.
For the two index patients, no correlation was observed between RICVs and OARs doses. However for those patients mean(maximum) LETd values in the affected OARs were up to 4.0 ± 0.4 (7.8 ± 0.1)keV/μm; those LETd values were significantly higher (p = 0.02) than the mean(maximum) LETd values for the rest of the cohort (mean: 3.1 ± 0.3, maximum: 4.8 ± 1.0 keV/μm). This was due to asymmetric field arrangement, thus resulting in marked asymmetric LETd distributions. For such arrangement, maximum LETd values variations in vascular structures due to range uncertainties were up to 1.2 keV/μm, whilst for the symmetric one they were up to 0.7 keV/μm.
For children with and without RICVs, quantitative analysis showed a significant correlation with LETd average/maximum values in vascular structures, whilst no correlation was found on dosimetric parameters.
本研究分析了接受笔形束扫描（PBS）质子治疗（PT）的儿童颅咽管瘤（CP）患者中有无放射性诱导的脑血管病变（RICV）的剂量学和平均线性能量传递（LETd）相关性。
我们回顾了 16 例接受 PT 治疗的 CP 患者的系列病例，中位剂量为 54 Gy（RBE）。两名（12.5%）索引患者在 PT 后 14 和 24 个月（中位数 19 个月）出现 RICV。基于 PT 前后的 CT 和 MRI 对双侧颈内动脉（ICAs）和 Willis 环等危及器官（OARs）进行了轮廓描绘。对剂量学进行了回顾，并计算了 LETd 分布；分析了 PTV 和 OAR 的 LETd 指标。对于亚组，计算了由于射程不确定性导致的剂量学和 LETd 值的稳健性。
对于两名索引患者，未观察到 RICV 与 OARs 剂量之间的相关性。然而，对于这些患者，受影响的 OARs 中的平均（最大）LETd 值高达 4.0±0.4（7.8±0.1）keV/μm；这些 LETd 值明显高于（p=0.02）其余队列的平均（最大）LETd 值（平均：3.1±0.3，最大：4.8±1.0 keV/μm）。这是由于非对称的射野布置，从而导致了明显的非对称 LETd 分布。对于这种布置，由于射程不确定性，血管结构中最大 LETd 值的变化高达 1.2 keV/μm，而对于对称布置，其变化高达 0.7 keV/μm。
对于有无 RICV 的儿童，定量分析显示与血管结构中的平均/最大 LETd 值有显著相关性，而在剂量学参数上则没有相关性。
