Purpose: Brain metastases occur in up to 30% of patients with advanced cancer and remain a major clinical challenge. While WBRT was historically the standard treatment, it provided limited survival benefit and significant neurocognitive toxicity, leading to increasing use of stereotactic radiosurgery (SRS). Recent advances with single-isocenter, multi-target (SIMT) dynamic conformal arc (DCA) techniques on modern linear accelerators have enabled efficient treatment of numerous lesions within a single session, though concerns regarding geometric accuracy persist. This study aimed to evaluate local control outcomes and influencing factors following DCA-SIMT radiosurgery in patients with multiple brain metastases. Methods: We retrospectively analyzed 195 brain metastases treated using single-isocenter, multi-target dynamic conformal arc (DCA-SIMT) stereotactic radiosurgery on a Varian TrueBeam LINAC between August 2018 and September 2020. Treatment planning was performed with Brainlab Elements MultiMets software, version 2.0 and image guidance with ExacTrac. Local control was assessed on MRI according to BM-RANO criteria, while radiation-induced contrast enhancements (RICE) were identified using multiparametric MRI. The median follow-up duration was 12 months. Statistical analyses included chi-square and ROC analyses, withp< 0.05 considered statistically significant. Results: A total of 195 brain metastases in 37 patients were analyzed. Local control at 6 months was achieved in 93% of lesions, with complete or partial response in 82%. Distance-to-isocenter (DTI), gradient index (GI), and target volume (GTV/PTV) were not associated with local control. In contrast, conformity index (CI) < 1.42 predicted better treatment response (AUC = 0.698,p= 0.0006). Margin expansion ≥ 0.5 mm was associated with improved local control (p= 0.049), while higher margins did not further improve outcomes. Prescription dose showed no significant impact. The addition of immunotherapy or targeted therapy within 4 months post-SRS significantly increased the likelihood of radiographic response (OR = 2.55,p= 0.030), with the strongest association observed in lung adenocarcinoma patients (p< 0.001). Conclusions: DCA-SIMT stereotactic radiosurgery achieves high local control in patients with multiple brain metastases. Conformity index, minimal margin expansion, and systemic therapy influenced outcomes, whereas distance-to-isocenter and dose did not. Further validation is needed to optimize margins in high-DTI scenarios.
目的：晚期癌症患者中高达30%会发生脑转移，这仍是临床面临的主要挑战。全脑放疗曾为传统标准疗法，但其生存获益有限且神经认知毒性显著，促使立体定向放射外科治疗的应用日益广泛。现代直线加速器单等中心多靶区动态适形弧技术的最新进展，使得单次治疗多个病灶成为可能，但其几何精度问题仍受关注。本研究旨在评估多发性脑转移患者接受动态适形弧单等中心多靶区放射外科治疗后的局部控制效果及其影响因素。 方法：回顾性分析2018年8月至2020年9月期间，使用瓦里安TrueBeam直线加速器通过单等中心多靶区动态适形弧技术治疗的195个脑转移灶。治疗计划采用Brainlab Elements MultiMets 2.0版软件制定，影像引导使用ExacTrac系统。根据脑转移瘤疗效评估标准通过磁共振成像评估局部控制情况，同时采用多参数磁共振识别放射性对比剂增强反应。中位随访时间为12个月。统计分析包括卡方检验和受试者工作特征曲线分析，以p<0.05为统计学显著标准。 结果：共分析37例患者的195个脑转移灶。6个月局部控制率达93%，其中82%病灶达到完全或部分缓解。等中心距离、梯度指数及靶区体积与局部控制无显著关联。而适形指数<1.42可预测更好的治疗反应（曲线下面积=0.698，p=0.0006）。边界外扩≥0.5毫米与改善的局部控制相关（p=0.049），但更大外扩未带来额外获益。处方剂量无显著影响。放射外科治疗后4个月内联合免疫治疗或靶向治疗显著提高影像学缓解概率（比值比=2.55，p=0.030），在肺腺癌患者中关联性最强（p<0.001）。 结论：动态适形弧单等中心多靶区立体定向放射外科治疗在多发性脑转移患者中可实现较高的局部控制率。适形指数、最小边界外扩及系统治疗是影响疗效的关键因素，而等中心距离和剂量则无显著影响。未来需进一步验证以优化高距离-等中心比场景下的边界设定。
Local Control After Single-Isocenter Dynamic Conformal Arc SRS for Brain Metastases
肿瘤(癌症)患者之家