Acker Gueliz, Nachbar Marcel, Soffried Nina, Bodnar Bohdan, Janas Anastasia, Krantchev Kiril, Kalinauskaite Goda, Kluge Anne, Shultz David, Conti Alfredo, Kaul David, Zips Daniel, Vajkoczy Peter, Senger Carolin
Department of Neurosurgery, Charité-Universitätsmedizin Berlin (Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health), Berlin, Germany.
Berlin Institute of Health at Charité - Universitätsmedizin Berlin, BIH Academy, Clinician Scientist Program, Berlin, Germany.
Front Oncol. 2023 Mar 16;13:1056330. doi: 10.3389/fonc.2023.1056330. eCollection 2023.
Neoadjuvant stereotactic radiosurgery (NaSRS) of brain metastases has gained importance, but it is not routinely performed. While awaiting the results of prospective studies, we aimed to analyze the changes in the volume of brain metastases irradiated pre- and postoperatively and the resulting dosimetric effects on normal brain tissue (NBT).
We identified patients treated with SRS at our institution to compare hypothetical preoperative gross tumor and planning target volumes (pre-GTV and pre-PTV) with original postoperative resection cavity volumes (post-GTV and post-PTV) as well as with a standardized-hypothetical PTV with 2.0 mm margin. We used Pearson correlation to assess the association between the GTV and PTV changes with the pre-GTV. A multiple linear regression analysis was established to predict the GTV change. Hypothetical planning for the selected cases was created to assess the volume effect on the NBT exposure. We performed a literature review on NaSRS and searched for ongoing prospective trials.
We included 30 patients in the analysis. The pre-/post-GTV and pre-/post-PTV did not differ significantly. We observed a negative correlation between pre-GTV and GTV-change, which was also a predictor of volume change in the regression analysis, in terms of a larger volume change for a smaller pre-GTV. In total, 62.5% of cases with an enlargement greater than 5.0 cm were smaller tumors (pre-GTV < 15.0 cm), whereas larger tumors greater than 25.0 cm showed only a decrease in post-GTV. Hypothetical planning for the selected cases to evaluate the volume effect resulted in a median NBT exposure of only 67.6% (range: 33.2-84.5%) relative to the dose received by the NBT in the postoperative SRS setting. Nine published studies and twenty ongoing studies are listed as an overview.
Patients with smaller brain metastases may have a higher risk of volume increase when irradiated postoperatively. Target volume delineation is of great importance because the PTV directly affects the exposure of NBT, but it is a challenge when contouring resection cavities. Further studies should identify patients at risk of relevant volume increase to be preferably treated with NaSRS in routine practice. Ongoing clinical trials will evaluate additional benefits of NaSRS.
脑转移瘤的新辅助立体定向放射外科治疗（NaSRS）已变得愈发重要，但尚未常规开展。在等待前瞻性研究结果期间，我们旨在分析脑转移瘤术前和术后照射体积的变化以及对正常脑组织（NBT）产生的剂量学效应。
我们确定了在本机构接受立体定向放射外科治疗的患者，以比较假设的术前大体肿瘤体积和计划靶体积（术前GTV和术前PTV）与术后原始切除腔体积（术后GTV和术后PTV），以及与有2.0毫米边缘的标准化假设PTV。我们使用Pearson相关性来评估GTV和PTV变化与术前GTV之间的关联。建立多元线性回归分析以预测GTV变化。为所选病例创建假设计划以评估对NBT照射的体积效应。我们对NaSRS进行了文献综述并搜索了正在进行的前瞻性试验。
我们纳入了30例患者进行分析。术前/术后GTV和术前/术后PTV无显著差异。我们观察到术前GTV与GTV变化之间呈负相关，在回归分析中这也是体积变化的一个预测指标，即术前GTV越小，体积变化越大。总体而言，62.5%体积增大超过5.0立方厘米的病例为较小肿瘤（术前GTV<15.0立方厘米），而大于25.0立方厘米的较大肿瘤术后GTV仅减小。为所选病例评估体积效应的假设计划显示，相对于术后立体定向放射外科治疗中NBT接受的剂量，NBT照射的中位值仅为67.6%（范围：33.2 - 84.5%）。列出了九项已发表研究和二十项正在进行的研究作为概述。
脑转移瘤较小的患者术后照射时体积增加的风险可能更高。靶体积勾画非常重要，因为PTV直接影响NBT的照射，但在勾勒切除腔时是一项挑战。进一步的研究应确定有相关体积增加风险的患者，以便在常规实践中优先采用NaSRS治疗。正在进行的临床试验将评估NaSRS的额外益处。
