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The 18F-labeled fibroblast activation protein inhibitor (FAPI) 18FFAPI-74 has the benefit of a higher synthetic yield and better image resolution than 68Ga-labeled FAPI. We preliminarily evaluated the diagnostic performance of 18FFAPI-74 PET in patients with various histopathologically confirmed cancers or suspected malignancies. Methods: We enrolled 31 patients (17 men and 14 women) with lung cancer (n = 7), breast cancer (n = 5), gastric cancer (n = 5), pancreatic cancer (n = 3), other cancers (n = 5), and benign tumors (n = 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. 18FFAPI-74 PET scanning was performed 60 min after the intravenous injection of 18FFAPI-74 (240 ± 31 MBq). The 18FFAPI-74 PET images were compared between the primary or local recurrent lesions of malignant tumors (n = 21) and nonmalignant lesions (n = 8: type-B1 thymomas, granuloma, solitary fibrous tumor, and postoperative or posttherapeutic changes). The uptake and number of detected lesions on 18FFAPI-74 PET were also compared with those on 18FFDG PET for available patients (n = 19). Results: 18FFAPI-74 PET showed higher uptake in primary lesions of various cancers than in nonmalignant lesions (median SUVmax, 9.39 range, 1.83-25.28 vs. 3.49 range, 2.21-15.58; P = 0.053), but some of the nonmalignant lesions showed high uptake. 18FFAPI-74 PET also showed significantly higher uptake than 18FFDG PET (median SUVmax, 9.44 range, 2.50-25.28 vs. 5.45 range, 1.22-15.06 in primary lesions P = 0.010, 8.86 range, 3.51-23.33 vs. 3.84 range, 1.01-9.75 in lymph node metastases P = 0.002, and 6.39 range, 0.55-12.78 vs. 1.88 range, 0.73-8.35 in other metastases P = 0.046, respectively). In 6 patients, 18FFAPI-74 PET detected more metastatic lesions than 18FFDG PET. Conclusion: 18FFAPI-74 PET showed higher uptake and detection rates in primary and metastatic lesions than did 18FFDG PET. 18FFAPI-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, 18F-labeled FAPI ligand might serve a higher demand in clinical care in the future.
Watabe et al. (Fri,) studied this question.