Lægdsmand Peter, Matysiak Witold, Muren Ludvig P, Lassen-Ramshad Yasmin, Maduro John H, Vestergaard Anne, Righetto Roberto, Pettersson Erik, Kristensen Ingrid, Dutheil Pauline, Demoor-Goldschmidt Charlotte, Charlwood Frances, Whitfield Gillian, Feijoo Marta M, Vela Anthony, Missohou Fernand, Vennarini Sabina, Mirandola Alfredo, Orlandi Ester, Rombi Barbara, Goedgebeur Anneleen, Van Beek Karen, Bannink-Gawryszuk Agata, Campoo Fernando C, Engellau Jacob, Toussaint Laura
Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus N, Denmark.
Aarhus University, Department of Clinical Medicine, Aarhus N, Denmark.
Phys Imaging Radiat Oncol. 2024 Nov 11;32:100675. doi: 10.1016/j.phro.2024.100675. eCollection 2024 Oct.
Radiotherapy for paediatric posterior fossa tumours may cause complications in the brainstem and upper spinal cord due to high doses. With proton therapy (PT) this risk may increase due to higher relative biological effectiveness (RBE) from elevated linear energy transfer (LET). This study assesses variations in LET in the brainstem and spinal cord in proton treatment plans from European centres.
Ten European PT centres using spot-scanning PT planned two paediatric posterior fossa cases: One overlapping partly with the brainstem and upper spinal cord, prescribed 54 Gy(RBE), and the second wrapping around these organs, prescribed 59.4 Gy(RBE). Dose-averaged LET distributions were assessed in volumes of the brainstem and spinal cord irradiated to over 50 Gy(RBE = 1.1). The maximum hinge angle effect on near-maximum RBE-weighted doses using the Unkelbach RBE model was also investigated.
In the first case, the mean LET in brainstem volumes receiving more than 50 Gy(RBE = 1.1) ranged from 2.8 keV/µm to 3.6 keV/µm across centres (median: 3.3 keV/µm). In the second case, treatment plans showed a narrower range of mean LET in the brainstem, from 2.5 keV/µm to 2.8 keV/µm (median: 2.7 keV/µm). There was no statistically significant impact of the maximum hinge angle.
LET distributions vary across centres due to different techniques but are also influenced significantly by factors like shape and position of the target volume.
儿童后颅窝肿瘤放疗因高剂量可能导致脑干和脊髓出现并发症。对于质子治疗（PT），由于线性能量传递（LET）升高导致相对生物效应（RBE）更高，这种风险可能会增加。本研究评估了欧洲各中心质子治疗计划中脑干和脊髓LET的变化情况。
十个使用点扫描质子治疗的欧洲中心针对两例儿童后颅窝病例制定计划：一例部分与脑干和上脊髓重叠，处方剂量为54 Gy（RBE），另一例围绕这些器官，处方剂量为59.4 Gy（RBE）。在接受超过50 Gy（RBE = 1.1）照射的脑干和脊髓体积中评估剂量平均LET分布。还研究了使用Unkelbach RBE模型时最大铰链角对接近最大RBE加权剂量的影响。
在第一个病例中，各中心接受超过50 Gy（RBE = 1.1）照射的脑干体积中的平均LET范围为2.8 keV/µm至3.6 keV/µm（中位数：3.3 keV/µm）。在第二个病例中，治疗计划显示脑干中的平均LET范围更窄，为2.5 keV/µm至2.8 keV/µm（中位数：2.7 keV/µm）。最大铰链角没有统计学上的显著影响。
由于技术不同，LET分布在各中心之间存在差异，但也受到靶区体积的形状和位置等因素的显著影响。
