手术性脑转移的立体定向放射外科（SRS）通常在切除手术后的1到6周内进行。术前与术后SRS给药时间与手术相关的问题仍然是一个关键问题，因为后者可能导致至多35%的患者出现乳膜病变（LMD）或放射性坏死。作者们在等待来自正在进行的临床一级数据之时，通过比较术后和模拟术前单剂量SRS剂量计划来填补这一空白，以治疗经手术切除的脑转移瘤患者。作者们在其机构数据库中回顾性地鉴定了2014年1月至2021年1月之间接受手术后伽马刀SRS（GKSRS）治疗的脑转移瘤术后患者。排除标准包括以前放射治疗、年龄<18岁和LMD先前诊断等。一旦确定，将设计一个模拟的术前SRS计划来治疗未切除的脑转移瘤，并与根据Radiation Therapy Oncology Group (RTOG) 90-05指南给予切除腔标准术后治疗进行对比。然后，通过使用配对统计分析进行多种术前和术后GKSRS治疗参数的比较。 作者们的研究对象包括45名接受GKSRS治疗的脑转移瘤切除术后患者，其中位年龄为59岁。主要癌症来源包括结直肠癌（27%）、非小细胞肺癌（22%）、乳腺癌（11%）、黑色素瘤（11%）和其他癌症（29%）。平均肿瘤和切除腔体积分别为15.06 cm3和12.61 cm3。在配对比较中，两组计划处理体积之间没有显著差异。当作者们比较了接受12 Gy或更多剂量（V12Gy）的周围脑组织体积，这是放射性坏死的重要预测因子时，术后SRS组（29/45，p = 0.008）的患者计划中有64%的患者录得了更大的V12体积。与术后计划相比，术前计划更加符合治疗区域（p < 0.001），并在病灶边缘呈现更陡的剂量下降（p = 0.0018）。 比较模拟的术前和实施的术后治疗计划的结果表明，术前SRS与术后计划相比，可以更好地覆盖病灶，剂量下降更为陡峭。此外，术前GKSRS计划中的V12Gy较低，这可能解释了先前回顾性研究中放射性坏死发生率的降低。

Stereotactic radiosurgery (SRS) for operative brain metastasis (BrM) is usually administered 1 to 6 weeks after resection. Preoperative versus postoperative timing of SRS delivery related to surgery remains a critical question, as a pattern of failure is the development of leptomeningeal disease (LMD) in as many as 35% of patients who undergo postoperative SRS or the occurrence of radiation necrosis. As they await level I clinical data from ongoing trials, the authors aimed to bridge the gap by comparing postoperative with simulated preoperative single-fraction SRS dosimetry plans for patients with surgically resected BrM.The authors queried their institutional database to retrospectively identify patients who underwent postoperative Gamma Knife SRS (GKSRS) after resection of BrM between January 2014 and January 2021. Exclusion criteria were prior radiation delivered to the lesion, age < 18 years, and prior diagnosis of LMD. Once identified, a simulated preoperative SRS plan was designed to treat the unresected BrM and compared with the standard postoperative treatment delivered to the resection cavity per Radiation Therapy Oncology Group (RTOG) 90-05 guidelines. Numerous comparisons between preoperative and postoperative GKSRS treatment parameters were then made using paired statistical analyses.The authors' cohort included 45 patients with a median age of 59 years who were treated with GKSRS after resection of a BrM. Primary cancer origins included colorectal cancer (27%), non-small cell lung cancer (22%), breast cancer (11%), melanoma (11%), and others (29%). The mean tumor and cavity volumes were 15.06 cm3 and 12.61 cm3, respectively. In a paired comparison, there was no significant difference in the planned treatment volumes between the two groups. When the authors compared the volume of surrounding brain that received 12 Gy or more (V12Gy), an important predictor of radiation necrosis, 64% of patient plans in the postoperative SRS group (29/45, p = 0.008) recorded greater V12 volumes. Preoperative plans were more conformal (p < 0.001) and exhibited sharper dose drop-off at the lesion margins (p = 0.0018) when compared with postoperative plans.Comparison of simulated preoperative and delivered postoperative SRS plans administered to the BrM or resection cavity suggested that preoperative SRS allows for more highly conformal lesional coverage and sharper dose drop-off compared with postoperative plans. Furthermore, V12Gy was lower in the presurgical GKSRS plans, which may account for the decreased incidence of radiation necrosis seen in prior retrospective studies.