Table 1_Mapping the physical topology of the tumor immune microenvironment: macroscopic image fractals as surrogate markers for immune exclusion phenotype and treatment resistance in colorectal cancer liver metastases.docx

To overcome biopsy sampling bias, this study investigates multimodal macroscopic image fractal dynamics to non-invasively map immune physical barriers and metabolic states, constructing a multi-scale immune-radiomics joint score (IRJS) for robust prognostic stratification and exploratory assessment of treatment resistance.</p>Materials and methods<p>This dual-center observational study enrolled 270 CRLM patients with dual-modality imaging (contrast-enhanced magnetic resonance imaging, CE-MRI, 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed-tomography, ¹⁸F-FDG PET/CT) and digital spatial pathology.

Patients were spatiotemporally divided into training (n=150), prospective temporal validation (n=45), and external validation (n=75) cohorts. Structural (FD_MRI) and metabolic (FD_PET) fractal dimensions were combined with the systemic immune-inflammation index (SII) and KRAS status to build the IRJS using XGBoost, utilizing the SHAP framework to evaluate mapping mechanisms.</p>Results<p>FD_MRI positively correlated with α-SMA⁺ pro-fibrotic stromal density (r = 0.684), which may reflect the mechanical barrier excluding CD8⁺ T cells.