A Dutch multicenter trial will test whether [18F]F-FAPI PET-CT can locate primary tumors in adults with cancer of unknown primary after standard imaging is inconclusive. The study plans to enroll 50 patients and uses the metabolic imaging approach to guide diagnostic workups that often stall due to negative or ambiguous initial tests. If the trial confirms clinical utility, FAPI PET-CT could reduce time to diagnosis and downstream treatment selection in a patient group where diagnostic delays can translate into worse outcomes. The trial design also reflects the expanding role of fibroblast activation protein (FAP) targeting in PET workflows. For biotech stakeholders, the value proposition is straightforward: improved detection rates and earlier treatment decisions can influence real-world imaging demand, reimbursement pathways, and future trial designs for FAP-targeted radiopharmaceuticals.