Schuermann Michaela, Dzierma Yvonne, Nuesken Frank, Oertel Joachim, Rübe Christian, Melchior Patrick
Department of Radiotherapy and Radiation Oncology, Saarland University Hospital, Homburg, Germany.
Faculty of Medicine, Saarland University, Saarbrücken, Germany.
Front Neurol. 2022 Jan 14;12:787140. doi: 10.3389/fneur.2021.787140. eCollection 2021.
Navigated transcranial magnetic stimulation (nTMS) of the motor cortex has been successfully implemented into radiotherapy planning by a number of studies. Furthermore, the hippocampus has been identified as a radiation-sensitive structure meriting particular sparing in radiotherapy. This study assesses the joint protection of these two eloquent brain regions for the treatment of glioblastoma (GBM), with particular emphasis on the use of automatic planning.
Patients with motor-eloquent brain glioblastoma who underwent surgical resection after nTMS mapping of the motor cortex and adjuvant radiotherapy were retrospectively evaluated. The radiotherapy treatment plans were retrieved, and the nTMS-defined motor cortex and hippocampus contours were added. Four additional treatment plans were created for each patient: two manual plans aimed to reduce the dose to the motor cortex and hippocampus by manual inverse planning. The second pair of re-optimized plans was created by the Auto-Planning algorithm. The optimized plans were compared with the "Original" plan regarding plan quality, planning target volume (PTV) coverage, and sparing of organs at risk (OAR).
A total of 50 plans were analyzed. All plans were clinically acceptable with no differences in the PTV coverage and plan quality metrics. The OARs were preserved in all plans; however, overall the sparing was significantly improved by Auto-Planning. Motor cortex protection was feasible and significant, amounting to a reduction in the mean dose by >6 Gy. The dose to the motor cortex outside the PTV was reduced by >12 Gy (mean dose) and >5 Gy (maximum dose). The hippocampi were significantly improved (reduction in mean dose: ipsilateral >6 Gy, contralateral >4.6 Gy; reduction in maximum dose: ipsilateral >5 Gy, contralateral >5 Gy). While the dose reduction using Auto-Planning was generally better than by manual optimization, the radiated total monitor units were significantly increased.
Considerable dose sparing of the nTMS-motor cortex and hippocampus could be achieved with no disadvantages in plan quality. Auto-Planning could further contribute to better protection of OAR. Whether the improved dosimetric protection of functional areas can translate into improved quality of life and motor or cognitive performance of the patients can only be decided by future studies.
多项研究已成功将运动皮层的导航经颅磁刺激（nTMS）应用于放射治疗计划。此外，海马体已被确定为放射敏感结构，在放射治疗中值得特别保护。本研究评估了在胶质母细胞瘤（GBM）治疗中对这两个明确脑区的联合保护，尤其强调自动计划的应用。
对运动功能区脑胶质母细胞瘤患者进行回顾性评估，这些患者在运动皮层nTMS映射后接受了手术切除及辅助放疗。检索放疗治疗计划，并添加nTMS定义的运动皮层和海马体轮廓。为每位患者额外创建四个治疗计划：两个手动计划，旨在通过手动逆向计划降低运动皮层和海马体的剂量。第二对重新优化的计划由自动计划算法创建。将优化后的计划与“原始”计划在计划质量、计划靶体积（PTV）覆盖范围和危及器官（OAR）保护方面进行比较。
共分析了50个计划。所有计划在临床上均可接受，PTV覆盖范围和计划质量指标无差异。所有计划中OAR均得到保护；然而，总体而言，自动计划显著改善了保护效果。运动皮层保护是可行且显著的，平均剂量降低超过6 Gy。PTV外运动皮层的剂量降低超过12 Gy（平均剂量）和超过5 Gy（最大剂量）。海马体的保护也显著改善（平均剂量降低：同侧超过6 Gy，对侧超过4.6 Gy；最大剂量降低：同侧超过5 Gy，对侧超过5 Gy）。虽然使用自动计划的剂量降低通常优于手动优化，但辐射的总监测单位显著增加。
在不影响计划质量的情况下，可以实现对nTMS运动皮层和海马体的显著剂量节省。自动计划可进一步有助于更好地保护OAR。功能区剂量学保护的改善是否能转化为患者生活质量以及运动或认知表现的改善，只能由未来的研究来决定。
