The efficacy of linac-based SRS/fSRS treatments using the single-isocenter coplanar FFF-VMAT technique for both single and multiple BM was investigated. Seventy patients (129 BM) treated with 15–21 Gy in 1 (n= 59) or 27 Gy in 3 (n= 11) fractions were analyzed. For each fraction, plans involving the intra-fractional errors measured by post-treatment CBCT were recalculated. The relationships of BM size, distance-to-isocenter, and barycenter shift with the difference in target coverage were evaluated. Clinical outcomes were assessed using logistic regression and Kaplan-Meier analysis. The median delivery time was 3.78 min (range, 1.83–9.25). The median post-treatment 3D error was 0.5 mm (range, 0.1–2.7) and the maximum rotational error was 0.3° (range, 0.0–1.3). In single BM patients, the GTV D95% was never reduced by >5%, whereas PTV D95% reductions >1% occurred in only 11 cases (29%). In multiple BM patients, dose deficits >5% and >1% occurred in 2 GTV (2%) and 34 PTV (37%), respectively. The differences in target coverage showed a moderate-to-strong correlation only with barycenter shift. Local failure of at least one treated BM occurred in 13 (21%) patients and the 1-year and 2-year local control rates for all lesions were 94% and 90%, respectively. The implemented workflow ensured that the degradation of target and brain dose metrics in delivered treatments was negligible. Along with encouraging clinical outcomes, these findings warrant a reduction in the PTV margins at our institution.
本研究探讨了基于直线加速器的立体定向放射外科/分次立体定向放射治疗（SRS/fSRS）采用单等中心共面FFF-VMAT技术治疗单发及多发脑转移瘤（BM）的疗效。共分析了70例患者（129个脑转移灶），其中59例接受单次15–21 Gy照射，11例接受3次共27 Gy照射。针对每次治疗，根据治疗后锥形束CT（CBCT）测得的分次内误差重新计算了治疗计划。评估了脑转移灶大小、与等中心的距离以及质心偏移与靶区覆盖度差异之间的关系。临床结局采用逻辑回归和Kaplan-Meier分析进行评估。中位照射时间为3.78分钟（范围：1.83–9.25）。治疗后三维误差中位数为0.5毫米（范围：0.1–2.7），最大旋转误差为0.3°（范围：0.0–1.3）。在单发脑转移患者中，GTV D95%从未降低超过5%，而PTV D95%降低超过1%仅发生在11例（29%）中。在多发脑转移患者中，剂量不足超过5%和超过1%分别发生在2个GTV（2%）和34个PTV（37%）。靶区覆盖度的差异仅与质心偏移呈中度至强相关。13例（21%）患者出现至少一个治疗脑转移灶的局部失败，所有病灶的1年和2年局部控制率分别为94%和90%。所实施的工作流程确保了实际治疗中靶区和脑部剂量指标的劣化可忽略不计。结合令人鼓舞的临床结果，这些发现支持在本机构缩小PTV外放边界。
肿瘤(癌症)患者之家