Longitudinal radiomics of liver metastases during magnetic resonance-guided radiotherapy.

Abstract

Background and purposeMagnetic resonance-guided radiotherapy (MRgRT) offers high-quality soft tissue contrast and treatment monitoring, supporting longitudinal radiomics analysis. We investigated treatment-related radiomic changes during stereotactic body radiotherapy (SBRT) for liver metastases and healthy liver.Materials and methodsFeatures were extracted from the gross tumour volume (GTV) and five 2-cm liver rings around the planning target volume (PTV) in 34 patients treated with five-fraction MRgSBRT. Features showing changes below baseline variability or high correlation (Spearman's |r| > 0.9) were excluded, with pre-treatment values averaged into a robust baseline. Linear regression slopes informed uniform manifold approximation and projection (UMAP) followed by hierarchical density-based spatial clustering of applications with noise (HDBSCAN) for patient stratification, with false discovery rate-corrected Kruskal-Wallis testing identifying representative features. Correlations with GTV volume and mean cumulative liver-ring dose were evaluated.ResultsOf 160 GTV features, 55 uncorrelated features remained. Three patient groups (n = 4, 10, and 20) with distinct longitudinal patterns were identified. Intensity-based energy showed significant differences across patient groups (adjusted p = 0.001), weakly correlated (|r| volume in the two larger groups. In the innermost liver ring, 49 uncorrelated features were analysed. Two patient groups (n = 19 and 15) were identified, with intensity-based energy, mean intensity, and maximum intensity showing significant group differences, weakly correlated with mean cumulative dose.ConclusionsThis longitudinal MR-based radiomics framework identified GTV and healthy liver patient groups, with distinct treatment-related feature changes. This pipeline could be extended to integrate treatment response assessment in future studies.