BACKGROUND: B7-H3 is a promising target for cancer therapy, notably in prostate cancer (PCa), particularly in metastatic, castration-resistant PCa (mCRPC). With the development of B7-H3-targeted therapies, there is a need for a rapid, reliable, and cost-effective method to detect and monitor B7-H3 expression. Leveraging their abundance and stability, we developed a liquid biopsy assay using extracellular vesicles (EVs) for this purpose. METHODS: B7-H3 RESULTS: The assay detected higher B7-H3 CONCLUSIONS: This B7-H3