Researchers from the DQBM Bodenmiller Lab used imaging mass cytometry to map more than 1.1 million cells across 44 melanoma brain metastasis samples. Patients responding to immune checkpoint inhibitors showed localized, clustered immune patterns and higher proportions of several T cell subsets, B cells and IDO-positive macrophages.
Localized CD8-positive T cell infiltration was associated with longer survival, even when overall T cell abundance was similar. In contrast, neutrophil-rich tumours correlated with treatment resistance and poorer outcomes. The findings indicate that spatial immune architecture could complement clinical markers when stratifying patients for immunotherapy, although prospective validation remains necessary.