Background: The aim of this study was to investigate the role of clinical, dosimetric and pretherapeutic magnetic resonance imaging (MRI) features for lesion-specific outcome prediction of stereotactic radiotherapy (SRT) in patients with brain metastases from malignant melanoma (MBM). Methods: In this multicenter, retrospective analysis, we reviewed 517 MBM from 130 patients treated with SRT (single fraction or hypofractionated). For each gross tumor volume (GTV) 1576 radiomic features (RF) were calculated (788 each for the GTV and for a 3 mm margin around the GTV). Clinical parameters, radiation dose and RF from pretherapeutic contrast-enhanced T1-weighted MRI from different institutions were evaluated with a feature processing and elimination pipeline in a nested cross-validation scheme. Results: Seventy-two (72) of 517 lesions (13.9%) showed a local failure (LF) after SRT. The processing pipeline showed clinical, dosimetric and radiomic features providing information for LF prediction. The most prominent ones were the correlation of the gray level co-occurrence matrix of the margin (hazard ratio (HR): 0.37, confidence interval (CI): 0.23-0.58) and systemic therapy before SRT (HR: 0.55, CI: 0.42-0.70). The majority of RF associated with LF was calculated in the margin around the GTV. Conclusions: Pretherapeutic MRI based RF connected with lesion-specific outcome after SRT could be identified, despite multicentric data and minor differences in imaging protocols. Image data analysis of the surrounding metastatic environment may provide therapy-relevant information with the potential to further individualize radiotherapy strategies.

翻译：背景：本研究旨在探讨临床特征、剂量学参数及治疗前磁共振成像（MRI）特征对恶性黑色素瘤脑转移患者立体定向放疗疗效的病灶特异性预测价值。方法：通过多中心回顾性分析，纳入130例接受立体定向放疗（单次或大分割方案）患者的517个脑转移灶。针对每个大体肿瘤体积，计算了1576个影像组学特征（其中GTV内部及GTV外缘3mm扩展区各788个）。采用嵌套交叉验证框架下的特征处理与筛选流程，评估了来自不同机构的治疗前增强T1加权MRI中的临床参数、放射剂量及影像组学特征。结果：517个病灶中72个（13.9%）在立体定向放疗后出现局部失败。特征处理流程显示临床、剂量学及影像组学特征对局部失败预测具有贡献，其中最具显著性的特征包括：GTV外缘灰度共生矩阵相关性（风险比：0.37，置信区间：0.23-0.58）以及放疗前全身治疗史（风险比：0.55，置信区间：0.42-0.70）。多数与局部失败相关的影像组学特征来源于GTV外缘区域。结论：尽管存在多中心数据及影像协议的细微差异，仍可识别出基于治疗前MRI的影像组学特征与立体定向放疗后病灶特异性疗效的关联。转移灶周围微环境的影像数据分析可提供具有临床指导价值的信息，有望推动放疗策略的个体化发展。