68Ga-FAPI-46 PET for imaging of FAP expressing cancer – a single-center prospective interventional single-arm clinical trial: study protocol and initial results

Ziel/Aim The fibroblast activation protein (FAP) is highly expressed on cells of the tumor or the tumor associated microenvironment and thus is an interesting target for imaging and therapy. Here we assess the diagnostic value of ⁶⁸Ga-FAPI-46 PET for various tumor entities.

Methodik/Methods This is a single-center prospective interventional non-randomized single-arm clinical phase 2 trial (NCT05160051). We will enroll n=155 patients to undergo ⁶⁸Ga-FAPI-46 and ¹⁸F-FDG PET/CT. Key inclusion criteria are: (a) proven or suspected malignant tumor, (b) imaging at initial staging or re-staging of disease, (c) at least one detectable tumor lesion with any diameter>1 cm, (d) intended or performed surgery or biopsy of tumor within 8 weeks before or after enrolment. Primary endpoint is the positive predictive value on a per-region- and per-patient-basis of ⁶⁸Ga-FAPI-46 PET for detection of tumor. Key secondary endpoints were (a) association between ⁶⁸Ga-FAPI-46 PET uptake intensity and histopathologic FAP expression, (b) accuracy of ⁶⁸Ga-FAPI-46 versus ¹⁸F-FDG PET, (c) impact on management, (d) inter-reader reproducibility, (e) safety, (f) change in staging/prognostic groups.

Ergebnisse/Results At submission, in total n=91 of 155 (59%) patients have been enrolled and n=88 underwent PET. Five most common tumor types were renal cell cancer (n=18/88, 20%), sarcoma (n=17/88, 19%), lung cancer (n=8/88, 9%), lymphoma (n=9/88, 10%), and PDAC (n=7/88, 8%). Patients were referred for initial staging (n=57/88, 65%) or re-staging (n=31/88, 35%) of disease. On clinical reads, any tumor was detected on ⁶⁸Ga-FAPI-46 versus ¹⁸F-FDG PET in n=88/88 (100%) versus 86/88 (98%) patients. Average SUV_max for ⁶⁸Ga-FAPI-46 versus ¹⁸F-FDG PET was 14.4 versus 15.2. Histopathology, follow-up and blinded reader assessments are pending.

Schlussfolgerungen/Conclusions This prospective interventional non-randomized single-arm clinical phase 2 trial was designed to assess the diagnostic value of ⁶⁸Ga-FAPI-46 versus ¹⁸F-FDG PET, impact on management, and inter-reader reproducibility for various types of tumor. Findings may support regulatory approval and identification of candidates for radioligand therapy.

Publication History

Article published online:
30 March 2023