Dzierma Yvonne, Schuermann Michaela, Melchior Patrick, Nuesken Frank, Oertel Joachim, Rübe Christian, Hendrix Philipp
Department of Radiotherapy and Radiation Oncology, Saarland University Medical Centre, Homburg, Germany.
Department of Neurosurgery, Saarland University Medical Centre and Saarland University Faculty of Medicine, Homburg, Germany.
Front Oncol. 2021 Feb 26;11:628007. doi: 10.3389/fonc.2021.628007. eCollection 2021.
Brain metastases can effectively be treated with surgical resection and adjuvant stereotactic radiotherapy (SRT). Navigated transcranial magnetic stimulation (nTMS) has been used to non-invasively map the motor cortex prior to surgery of motor eloquent brain lesions. To date, few studies have reported the integration of such motor maps into radiotherapy planning. The hippocampus has been identified as an additional critical structure of radiation-induced deficits. The aim of this study is to assess the feasibility of selective dose reduction to both the nTMS-based motor cortex and the hippocampi in SRT of motor-eloquent brain metastases. Patients with motor-eloquent brain metastases undergoing surgical resection and adjuvant SRT between 07/2014 and 12/2018 were retrospectively analyzed. The radiotherapy treatment plans were retrieved from the treatment planning system ("original" plan). For each case, two intensity-modulated treatment plans were created: the "motor" plan aimed to reduce the dose to the motor cortex, the "motor & hipp" plan additionally reduce the dose to the hippocampus. The optimized plans were compared with the "original" plan regarding plan quality, planning target volume (PTV) coverage, and sparing of organs at risk (OAR). 69 plans were analyzed, all of which were clinically acceptable with no significant differences for PTV coverage. All OAR were protected according to standard protocols. Sparing of the nTMS motor map was feasible: mean dose 9.66 ± 5.97 Gy (original) to 6.32 ± 3.60 Gy (motor) and 6.49 ± 3.78 Gy (motor & hipp), p<0.001. In the "motor & hipp" plan, dose to the ipsilateral hippocampi could be significantly reduced (max 1.78 ± 1.44 Gy vs 2.49 ± 1.87 Gy in "original", p = 0.003; mean 1.01 ± 0.92 Gy vs. 1.32 ± 1.07 Gy in "original", p = 0.007). The study confirms the results from previous studies that inclusion of nTMS motor information into radiotherapy treatment planning is possible with a relatively straightforward workflow and can achieve reduced doses to the nTMS-defined motor area without compromising PTV coverage. Furthermore, we demonstrate the feasibility of selective dose reduction to the hippocampus at the same time. The clinical significance of these optimized plans yet remains to be determined. However, with no apparent disadvantages these optimized plans call for further and broader exploration.
脑转移瘤可通过手术切除和辅助立体定向放射治疗（SRT）得到有效治疗。在对运动功能区明确的脑病变进行手术前，导航经颅磁刺激（nTMS）已被用于非侵入性地绘制运动皮层。迄今为止，很少有研究报道将此类运动图谱整合到放射治疗计划中。海马体已被确定为辐射诱导损伤的另一个关键结构。本研究的目的是评估在运动功能区明确的脑转移瘤的SRT中，对基于nTMS的运动皮层和海马体进行选择性剂量降低的可行性。对2014年7月至2018年12月期间接受手术切除和辅助SRT的运动功能区明确的脑转移瘤患者进行回顾性分析。从治疗计划系统中检索放射治疗计划（“原始”计划）。对于每个病例，创建了两个调强治疗计划：“运动”计划旨在降低对运动皮层的剂量，“运动&海马”计划额外降低对海马体的剂量。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）的保护方面进行比较。分析了69个计划，所有这些计划在临床上均可接受，PTV覆盖范围无显著差异。所有OAR均按照标准方案得到保护。对nTMS运动图谱的保护是可行的：平均剂量从“原始”计划的9.66±5.97 Gy降至“运动”计划的6.32±3.60 Gy和“运动&海马”计划的6.49±3.78 Gy，p<0.001。在“运动&海马”计划中，同侧海马体的剂量可显著降低（最大值1.78±1.44 Gy对比“原始”计划的2.49±1.87 Gy，p = 0.003；平均值1.01±0.92 Gy对比“原始”计划的1.32±1.07 Gy，p = 0.007）。该研究证实了先前研究的结果，即通过相对简单的工作流程将nTMS运动信息纳入放射治疗计划是可行的，并且可以在不影响PTV覆盖范围的情况下降低对nTMS定义的运动区域的剂量。此外，我们证明了同时对海马体进行选择性剂量降低的可行性。这些优化计划的临床意义仍有待确定。然而，由于没有明显的缺点，这些优化计划需要进一步更广泛的探索。
