[18F]F-FAPI PET/CT to Identify Carcinoma of hitherto Unknown Primary origin: improving minimally-invasive cancer diagnostics.

Status: Started april 2023, KWF funding

In this non-commercial, investigator-initiated and patient association-driven, multi-center, prospective clinical study we aim to show that F-FAPI PET/CT is a valuable novel diagnostic tool, particularly for detection of a primary tumor in patients with negative results from the standard diagnostic work-up including FDG PET/CT. To this end we will determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of F-FAPI PET/CT for the identification of the primary tumor in CUP. We will include 50 patients who have been diagnosed with CUP after the standard diagnostic work-up including FDG PET/CT. Patients will be recruited via specific outpatient clinics, which are, as off 2021, financially supported by Dutch health insurance companies. F-FAPI PET/CT will be read centrally by at least 2 independent nuclear medicine physicians/nuclear radiologists; the results from this centralized reading will be made available to the attending physician with an accompanying recommendation for additional diagnostics and/or treatment in regular clinical care from the CUP outpatient clinic or CUPPNL. Patients will then be followed for a maximum of 6 months in order to verify any diagnosis made and to record treatment initiated based on F-FAPI PET/CT. Results of the F-FAPI PET/CT will then be compared to the results from the preceding diagnostic work-up and will be discussed in a multidisciplinary truth committee consisting of at least two oncologists, a pathologist, a radiologist, a nuclear medicine physician and a methodologist. Identification of a primary tumor is considered a positive outcome of the use of F-FAPI PET/CT. Subgroup analyses will be made based on gender, age, tumor histology and site of metastasis and performance status (applicable if more than n=10 per subgroup). The adherence to recommendations based on the F-FAPI PET/CT as well as its additional value in terms of influence on patient management will be evaluated as exploratory endpoints.