Analysis of clinical, dosimetric and radiomic features for predicting local failure after stereotactic radiotherapy of brain metastases in malignant melanoma (2405.20825v2)

Abstract: Background: This study aimed to predict lesion-specific outcomes after stereotactic radiotherapy (SRT) in patients with brain metastases from malignant melanoma (MBM), using clinical, dosimetric pretherapeutic MRI data. Methods: In this multicenter retrospective study, 517 MBM from 130 patients treated with single-fraction or hypofractionated SRT across three centers were analyzed. From contrast-enhanced T1-weighted MRI, 1576 radiomic features (RF) were extracted per lesion - 788 from the gross tumor volume (GTV), 788 from a 3 mm peritumoral margin. Clinical data, radiation dose and RF from one center were used for feature selection and model development via nested cross-validation; external validation was performed using the other two centers. Results: Local failure occurred in 72 of 517 lesions (13.9%). Predictive models based on clinical data (model 1), RF (model 2), or both (model 3) achieved c-indices of 0.60 +/- 0.15, 0.65 +/- 0.11, and 0.65 +/- 0.12. RF-based models outperformed the clinical model, while dosimetric data alone were not predictive. Most predictive RF came from the peritumoral margin (92%) vs. GTV (76%). On the first external dataset, all models performed similarly (c-index: 0.60-0.63), but showed poor generalization on the second (c-index < 0.50), likely due to differences in patient characteristics and imaging protocols. Conclusions: Information extracted from pretherapeutic MRI, particularly from the peritumoral area, can support accurate prediction of lesion-specific outcomes after SRT in MBM. When combined with clinical data, these imaging-derived markers offer valuable prognostic insights. However, generalizability remains challenging by heterogeneity in patient populations and MRI protocols.