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Cancer-associated fibroblasts (CAFs) are crucial components of the tumor microenvironment. Fibroblast activation protein (FAP) is overexpressed in CAFs. FAP-targeted molecular imaging agents, including the FAP inhibitors (FAPIs) 04 and 46, have shown promising results in tumor diagnosis. However, these molecules have a relatively short tumor-retention time for peptide-targeted radionuclide therapy applications. We aimed to design a 68 Ga-labeled FAPI dimer, 68 Ga-DOTA-2P(FAPI) 2 , to optimize the pharmacokinetics and evaluate whether this form is more effective than its monomeric analogs. Methods: 68 Ga-DOTA-2P(FAPI) 2 was synthesized on the basis of the quinoline-based FAPI variant (FAPI-46), and its binding properties were assayed in CAFs. Preclinical pharmacokinetics were determined in FAP-positive patient-derived xenografts using small-animal PET and biodistribution experiments. The effective dosimetry of 68 Ga-DOTA-2P(FAPI) 2 was evaluated in 3 healthy volunteers, and PET/CT imaging of 68 Ga-FAPI-46 and 68 Ga-DOTA-2P(FAPI) 2 was performed on 3 cancer patients. Results: 68 Ga-DOTA-2P(FAPI) 2 was stable in phosphate-buffered saline and fetal bovine serum for 4 h. The FAPI dimer showed high affinity and specificity for FAP in vitro and in vivo. The tumor uptake of 68 Ga-DOTA-2P(FAPI) 2 was approximately 2-fold stronger than that of 68 Ga-FAPI-46 in patient-derived xenografts, whereas healthy organs showed low tracer uptake and fast body clearance. The effective dose of 68 Ga-DOTA-2P(FAPI) 2 was 1.19E-02 mSv/MBq, calculated using OLINDA. Finally, the PET/CT scans of the 3 cancer patients revealed higher intratumoral uptake of 68 Ga-DOTA-2P(FAPI) 2 than of 68 Ga-FAPI-46 in all tumor lesions (SUV max , 8.1-39.0 vs. 1.7-24.0, respectively; P < 0.001). Conclusion: 68 Ga-DOTA-2P(FAPI) 2 has increased tumor uptake and retention properties compared with 68 Ga-FAPI-46, and it could be a promising tracer for both diagnostic imaging and targeted therapy of malignant tumors with positive expression of FAP., (© 2022 by the Society of Nuclear Medicine and Molecular Imaging.)

Purpose: This study aimed to evaluate the potential utility of [ 68 Ga]Ga-FAPI-04 PET/CT for diagnosing primary and metastatic lesions in patients with liver cancer, as well as to compare it with contrast-enhanced CT (CE-CT), liver MRI, and [ 18 F]-FDG PET/CT., Methods: We performed a single-center post hoc retrospective analysis of data obtained from a prospective parent study (NCT04416165). This study included 34 patients diagnosed with or suspected hepatic lesions who underwent concomitant [ 68 Ga]Ga-FAPI-04 and [ 18 F]-FDG/CT scans. Moreover, these patients underwent liver MRI (n = 34) and CE-CT (n = 25). Histopathologic (n = 62) or radiographic follow-up (n = 128) served as the reference standard for the final diagnosis., Results: Among the 34 patients, 20, 12, and 2 patients presented with hepatocellular carcinomas, intrahepatic cholangiocarcinomas, and benign hepatic nodules, respectively. The sensitivities of CE-CT, MRI, [ 68 Ga]Ga-FAPI-04, and [ 18 F]-FDG/CT for detecting primary liver tumors were 96%, 100%, 96%, and 65%, respectively. Regarding the diagnosis of all intrahepatic lesions, the per-lesion detection rate of [ 68 Ga]Ga-FAPI-04 PET/CT was slightly lower than that of MRI (85% vs. 100%, P = 0.34) and significantly higher than that of [ 18 F]-FDG PET/CT (85% vs. 52%, P < 0.001). Regarding the diagnosis of all malignant lesions (including extrahepatic disease), the tumor detection rate of [ 68 Ga]Ga-FAPI-04 PET/CT was 87.4%, which was significantly higher than that of [ 18 F]-FDG PET/CT (65.0%, P < 0.001)., Conclusions: Our findings indicate that the sensitivity of [ 68 Ga]Ga-FAPI-04 PET/CT to correctly identify primary liver tumors and metastatic lesions is equivalent to that of CE-CT and liver MRI. Moreover, [ 68 Ga]Ga-FAPI-04 PET/CT is better at identifying liver lesions than [ 18 F]-FDG PET/CT, and its use may improve tumor staging, recurrence detection, and implementation of necessary treatment modifications.

Purpose: We evaluated the potential usefulness of [ 68 Ga]Ga-DOTA-FAPI-04 positron emission tomography/computed tomography (PET/CT) for the diagnosis of primary and metastatic lesions in various types of cancer, compared with [ 18 F] FDG PET/CT., Methods: A total of 75 patients with various types of cancer underwent contemporaneous [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F] FDG PET/CT either for an initial assessment or for recurrence detection. Tumour uptake was quantified by the maximum standard uptake value (SUV max ). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of [ 18 F] FDG and [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT were calculated and compared to evaluate the diagnostic efficacy., Results: The study cohort consisted of 75 patients (47 males and 28 females; median age, 61.5 years; age range, 32-85 years). Fifty-four patients with 12 different tumour entities underwent paired [ 68 Ga]Ga-DOTA-FAPI-04 and [ 18 F] FDG PET/CT for initial assessment, while the other 21 patients underwent paired scans for recurrence detection. [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT was able to clearly identify 12 types of malignant tumours with favourable tumour-to-background contrast, which resulted in a higher detection rate of primary tumours than did [ 18 F] FDG PET/CT (98.2% vs. 82.1%, P = 0.021). Meanwhile, [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT showed a better sensitivity than [ 18 F] FDG PET/CT in the detection of lymph nodes (86.4% vs. 45.5%, P = 0.004) and bone and visceral metastases (83.8% vs. 59.5%, P = 0.004)., Conclusion: [ 68 Ga]Ga-DOTA-FAPI-04 PET/CT showed a superior diagnostic efficacy than [ 18 F] FDG PET/CT for the diagnosis of primary and metastatic lesions in patients with various types of cancer, especially in identifying liver metastases, peritoneal carcinomatosis, and brain tumours.

Purpose: This study aimed to evaluate the potential utility of [68Ga]Ga-FAPI-04 PET/CT for diagnosing primary and metastatic lesions in patients with liver cancer, as well as to compare it with contrast-enhanced CT (CE-CT), liver MRI, and [18F]-FDG PET/CT. Methods: We performed a single-center post hoc retrospective analysis of data obtained from a prospective parent study (NCT04416165). This study included 34 patients diagnosed with or suspected hepatic lesions who underwent concomitant [68Ga]Ga-FAPI-04 and [18F]-FDG/CT scans. Moreover, these patients underwent liver MRI (n = 34) and CE-CT (n = 25). Histopathologic (n = 62) or radiographic follow-up (n = 128) served as the reference standard for the final diagnosis. Results: Among the 34 patients, 20, 12, and 2 patients presented with hepatocellular carcinomas, intrahepatic cholangiocarcinomas, and benign hepatic nodules, respectively. The sensitivities of CE-CT, MRI, [68Ga]Ga-FAPI-04, and [18F]-FDG/CT for detecting primary liver tumors were 96%, 100%, 96%, and 65%, respectively. Regarding the diagnosis of all intrahepatic lesions, the per-lesion detection rate of [68Ga]Ga-FAPI-04 PET/CT was slightly lower than that of MRI (85% vs. 100%, P = 0.34) and significantly higher than that of [18F]-FDG PET/CT (85% vs. 52%, P < 0.001). Regarding the diagnosis of all malignant lesions (including extrahepatic disease), the tumor detection rate of [68Ga]Ga-FAPI-04 PET/CT was 87.4%, which was significantly higher than that of [18F]-FDG PET/CT (65.0%, P < 0.001). Conclusions: Our findings indicate that the sensitivity of [68Ga]Ga-FAPI-04 PET/CT to correctly identify primary liver tumors and metastatic lesions is equivalent to that of CE-CT and liver MRI. Moreover, [68Ga]Ga-FAPI-04 PET/CT is better at identifying liver lesions than [18F]-FDG PET/CT, and its use may improve tumor staging, recurrence detection, and implementation of necessary treatment modifications. [ABSTRACT FROM AUTHOR]

Purpose: We evaluated the potential usefulness of [68Ga]Ga-DOTA-FAPI-04 positron emission tomography/computed tomography (PET/CT) for the diagnosis of primary and metastatic lesions in various types of cancer, compared with [18F] FDG PET/CT. Methods: A total of 75 patients with various types of cancer underwent contemporaneous [68Ga]Ga-DOTA-FAPI-04 and [18F] FDG PET/CT either for an initial assessment or for recurrence detection. Tumour uptake was quantified by the maximum standard uptake value (SUVmax). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of [18F] FDG and [68Ga]Ga-DOTA-FAPI-04 PET/CT were calculated and compared to evaluate the diagnostic efficacy. Results: The study cohort consisted of 75 patients (47 males and 28 females; median age, 61.5 years; age range, 32–85 years). Fifty-four patients with 12 different tumour entities underwent paired [68Ga]Ga-DOTA-FAPI-04 and [18F] FDG PET/CT for initial assessment, while the other 21 patients underwent paired scans for recurrence detection. [68Ga]Ga-DOTA-FAPI-04 PET/CT was able to clearly identify 12 types of malignant tumours with favourable tumour-to-background contrast, which resulted in a higher detection rate of primary tumours than did [18F] FDG PET/CT (98.2% vs. 82.1%, P = 0.021). Meanwhile, [68Ga]Ga-DOTA-FAPI-04 PET/CT showed a better sensitivity than [18F] FDG PET/CT in the detection of lymph nodes (86.4% vs. 45.5%, P = 0.004) and bone and visceral metastases (83.8% vs. 59.5%, P = 0.004). Conclusion: [68Ga]Ga-DOTA-FAPI-04 PET/CT showed a superior diagnostic efficacy than [18F] FDG PET/CT for the diagnosis of primary and metastatic lesions in patients with various types of cancer, especially in identifying liver metastases, peritoneal carcinomatosis, and brain tumours. [ABSTRACT FROM AUTHOR]