Department of Radiation Oncology, University of California, San Francisco, California.
Department of Radiation Oncology, University of California, San Francisco, California.
Pract Radiat Oncol. 2018 Nov-Dec;8(6):e369-e376. doi: 10.1016/j.prro.2018.06.004. Epub 2018 Jun 7.
A previous analysis showed that brain metastases that are treated with frameless stereotactic radiation surgery (SRS) and planned with magnetic resonance imaging (MRI) >14 days before SRS had worse local control (LC). To evaluate if worse LC may be due to unaccounted interval metastasis growth and radiosurgical marginal miss, we quantified growth before SRS on preradiosurgical imaging.
We reviewed data from patients who were treated with fixed-frame SRS for brain metastases at our institution between 2010 and 2013 and had pretreatment diagnostic brain MRI and SRS-planning MRI scans available. Metastases were contoured on the pretreatment MRI scan and the day-of-treatment planning MRI scan for volumetric comparison. Growth rates were calculated. Serial volumetric contour expansions on the pretreatment MRI scans were used to determine the minimum margin necessary to encompass the entire metastasis on day of the SRS. LC was estimated by Kaplan-Meier method.
Among 411 brain metastases in 165 patients, the time between pretreatment and treatment MRI was associated with metastasis growth (P < .001) with a mean growth rate of 0.02 ml/day (95% confidence interval, 0.01-0.03) and a 1.35-fold volume increase at 14 days. Time between MRI scans was associated with the amount of margin that was needed to target the entire brain metastasis volume on the day of the SRS (P < .001), as were volume of metastasis on the pre-treatment MRI (P < .001) and melanoma histology (P < .001). LC was not associated with growth rate among patients who underwent fixed-frame SRS.
Time between pretreatment MRI and SRS is associated with brain metastasis growth, but LC is not compromised when patients receive fixed-frame SRS with same-day MRI planning. Margins may be needed for metastases that are treated with frameless SRS to account for growth between the planning MRI and SRS delivery.
In this study, we quantify brain metastasis growth over time by taking advantage of the availability of 2 pretreatment magnetic resonance imaging scans taken at 2 time points among patients treated with frame-fixed radiation surgery. We found that metastasis growth is associated with time, initial metastasis size, melanoma histology, and concurrent chemotherapy. Performing serial margin expansions demonstrated factors that are associated with the amount of margin that is needed to target the entire metastasis on the day of radiation surgery.
先前的分析表明，在接受无框架立体定向放射外科（SRS）治疗的脑转移瘤患者中，如果在 SRS 前 14 天以上进行 MRI 成像计划，则局部控制（LC）较差。为了评估较差的 LC 是否可能是由于未考虑的间隔转移生长和放射外科边缘错过，我们在放射前成像上量化了 SRS 前的生长情况。
我们回顾了 2010 年至 2013 年期间在我们机构接受固定框架 SRS 治疗的脑转移瘤患者的数据，并获得了治疗前诊断性脑 MRI 和 SRS 计划 MRI 扫描。在治疗前 MRI 扫描和治疗当天的计划 MRI 扫描上对转移瘤进行轮廓描绘，进行容积比较。计算生长率。使用治疗前 MRI 扫描上的连续容积扩展来确定在 SRS 当天包含整个转移瘤所需的最小边缘。LC 通过 Kaplan-Meier 方法进行估计。
在 165 名患者的 411 个脑转移瘤中，治疗前和治疗 MRI 之间的时间与转移瘤生长相关（P <.001），平均生长率为 0.02ml/天（95%置信区间，0.01-0.03），14 天时体积增加了 1.35 倍。MRI 扫描之间的时间与 SRS 当天靶向整个脑转移瘤体积所需的边缘量有关（P <.001），与治疗前 MRI 上的转移瘤体积（P <.001）和黑色素瘤组织学（P <.001）有关。在接受固定框架 SRS 的患者中，生长率与 LC 无关。
治疗前 MRI 与 SRS 之间的时间与脑转移瘤的生长有关，但当患者接受当天进行 MRI 计划的固定框架 SRS 治疗时，LC 不会受到影响。对于无框架 SRS 治疗的转移瘤，可能需要边缘以弥补计划 MRI 与 SRS 输送之间的生长。
在这项研究中，我们通过利用在接受框架固定放射外科治疗的患者中进行的 2 次治疗前磁共振成像扫描，来量化随时间推移的脑转移瘤生长情况。我们发现，转移瘤的生长与时间、初始转移瘤大小、黑色素瘤组织学和同时进行的化疗有关。进行连续边缘扩展的演示表明，存在与在放射外科手术当天靶向整个转移瘤所需的边缘量相关的因素。
