Only if a correlation between the spleen-to-liver and spleen-to-blood ratios of [64Cu]Cu-NOTA-α-CXCR3 uptake of responders and non-responders can be observed, [64Cu]Cu-NOTA-α-CXCR3-based PET imaging may qualify as an imaging approach for assessing systemic T cell activation as a surrogate marker for tumor response to ICI therapy. Here, CXCR3 is linked to neoplasm.