Initial Evaluation of [F]FAPI-74 PET for Various Histopathologically Confirmed Cancers and Benign Lesions.

The F-labeled fibroblast activation protein inhibitor (FAPI) [F]FAPI-74 has the benefit of a higher synthetic yield and better image resolution than Ga-labeled FAPI. We preliminarily evaluated the diagnostic performance of [F]FAPI-74 PET in patients with various histopathologically confirmed cancers or suspected malignancies. We enrolled 31 patients (17 men and 14 women) with lung cancer ( = 7), breast cancer ( = 5), gastric cancer ( = 5), pancreatic cancer ( = 3), other cancers ( = 5), and benign tumors ( = 6). Twenty-seven of the 31 patients were treatment-naïve or preoperative, whereas recurrence was suspected in the remaining 4 patients. Histopathologic confirmation was obtained for the primary lesions of 29 of the 31 patients. In the remaining 2 patients, the final diagnosis was based on the clinical course. [F]FAPI-74 PET scanning was performed 60 min after the intravenous injection of [F]FAPI-74 (240 ± 31 MBq). The [F]FAPI-74 PET images were compared between the primary or local recurrent lesions of malignant tumors ( = 21) and nonmalignant lesions ( = 8: type-B1 thymomas, granuloma, solitary fibrous tumor, and postoperative or posttherapeutic changes). The uptake and number of detected lesions on [F]FAPI-74 PET were also compared with those on [F]FDG PET for available patients ( = 19). [F]FAPI-74 PET showed higher uptake in primary lesions of various cancers than in nonmalignant lesions (median SUV, 9.39 [range, 1.83-25.28] vs. 3.49 [range, 2.21-15.58]; = 0.053), but some of the nonmalignant lesions showed high uptake. [F]FAPI-74 PET also showed significantly higher uptake than [F]FDG PET (median SUV, 9.44 [range, 2.50-25.28] vs. 5.45 [range, 1.22-15.06] in primary lesions [ = 0.010], 8.86 [range, 3.51-23.33] vs. 3.84 [range, 1.01-9.75] in lymph node metastases [ = 0.002], and 6.39 [range, 0.55-12.78] vs. 1.88 [range, 0.73-8.35] in other metastases [ = 0.046], respectively). In 6 patients, [F]FAPI-74 PET detected more metastatic lesions than [F]FDG PET. [F]FAPI-74 PET showed higher uptake and detection rates in primary and metastatic lesions than did [F]FDG PET. [F]FAPI-74 PET is a promising novel diagnostic modality for various tumors, especially for precise staging before treatment, including characterization of tumor lesions before surgery. Moreover, F-labeled FAPI ligand might serve a higher demand in clinical care in the future.