Diffusion and contrast-enhancement MRI phenotypes predict immune cell infiltration in brain metastases

Motivation: Immune checkpoint inhibitors (ICIs) can promote immune cell infiltration and increase anti-tumoral immune response in brain metastases (BM). Imaging proxies of immune infiltration would facilitate ICI-response monitoring in BM. Goal(s): To test whether the combined assessment of diffusion and contrast-enhancement MRI phenotypes can provide insights into microscopic immune infiltration. Approach: We studied the associations of diffusion and contrast-enhancement MRI phenotypes with histological immune cell infiltration and with ICI-treatment statusResults: Correlation analysis showed that high diffusivity and pronounced contrast-enhancement were positively associated with increased immune cell infiltration and were more likely observed in ICI-treated lesions. Impact: Immune checkpoint inhibitors (ICIs) can promote immune cell infiltration and increase anti-tumoral immune response in brain metastases (BM). Diffusion and contrast-enhancement MRI phenotypes provide potential imaging biomarkers to non-invasively monitor tissue changes related to anti-tumoral immune response following ICIs.