A British Journal of Cancer study evaluated whether PET imaging can indicate if immunotherapy drugs actually reach their tumor targets. The approach addresses a practical clinical gap: most patients do not respond to immune checkpoint inhibitors, and clinicians have lacked a reliable way to verify target engagement in the tumor microenvironment for individual patients. By using imaging readouts tied to drug distribution and target interaction, the work points toward a potential route for stratification or adjustment of therapy. If validated, such imaging biomarkers could reduce guesswork around continued treatment when target delivery is unlikely. For immuno-oncology pipelines, the report underscores growing emphasis on pharmacodynamic verification beyond plasma drug levels. It also suggests a near-term pathway to personalize checkpoint inhibitor use based on in situ target access. (Story coverage source: study report.)