The additional role of [68Ga]Ga-FAPI-04 PET/CT in patients with unknown primary lesion with a negative or equivocal [18F]FDG.

PURPOSE: [18F]FDG PET/CT to detect unknown primary lesions is essential for clinical management but still has limitations. [68Ga]Ga-FAPI is a tumor-stromal imaging agent that provides a promising alternative to [18F]FDG for the assessment of malignancies. We aimed to investigate whether [68Ga]Ga-FAPI PET/CT has an additional role in identifying unknown primary lesions with negative or equivocal [18F] FDG PET/CT results. METHODS: This single-center prospective clinical study was conducted between March 2020 and March 2022 at Southwest Medical University Hospital. Patients underwent [18F]FDG PET/CT for the identification of unknown primary lesions. They underwent repeat [68Ga]Ga-FAPI PET/CT when [18F]FDG PET/CT results were negative or equivocal. Histopathological examination, surgery, or clinical follow-up (at least 3 months) for FAPI-positive lesions. The diagnostic efficacy of [68Ga]Ga-FAPI in identifying unknown primary lesions was evaluated. RESULTS: A total of 44 participants (median age, 57 ± 12 [SD]; 22 [50%] men) were evaluated. Thirteen of the 44 patients had equivocal [18F]FDG PET/CT findings, while the diagnosis was clear on [68Ga]Ga-FAPI PET/CT. [68Ga]Ga-FAPI PET/CT also revealed primary lesions in additional 17 patients with negative [18F]FDG PET/CT findings. In fourteen of 44 patients, no primary lesion was detected by either tracer. On this basis, we analyzed 94 lymph node metastatic lesions. The mean SUVmax of lymph node metastases on [68Ga] Ga-FAPI PET/CT and [18F]FDG PET/CT were 9.2 ± 5.1, 7.9 ± 4.8 (p = 0.03) and the mean TBR were 9.1 ± 5.2, 4.9 ± 3.1 (p < 0.01), respectively. CONCLUSION: [68Ga]Ga-FAPI PET/CT showed great potential for identifying unknown primary lesions and has the potential to improve the detection rate of unknown primary lesions with negative or equivocal for [18F]FDG findings. TRIAL REGISTRATION: ClinicalTrial.gov. Identifier: ChiCTR2100044131.

Comparison of 18F-MFBG PET/CT and 18F-FDG PET/CT Images of Metastatic Neuroblastoma.

ABSTRACT: Two children with neuroblastoma underwent tumor resection and postoperative chemotherapy. After treatment, they participated in a clinical trial and received 18F-MFBG and 18F-FDG PET/CT examinations. Although similar lesions were found in the 2 examinations, the uptake pattern was different. The lymph nodes and bone lesions had intense 18F-MFBG activity, whereas 18F-FDG uptake was not very impressive. The uptake of bone marrow by 18F-MFBG was significantly stronger than that by 18F-FDG. This case emphasizes that 18F-MFBG PET/CT is superior to 18F-FDG PET/CT in detecting the metastases of neuroblastoma.

Benign lesions with 68Ga-FAPI uptake: a retrospective study.

OBJECTIVES: Although FAPI, as a pan-tumor tracer, shows high expression in the malignancy imaging, FAPI uptake is also seen in some benign lesions. The purpose of this study was to retrospectively analyze the characteristics of benign lesions with FAPI uptake on 68Ga-FAPI PET/CT imaging. METHODS: The electronic medical and imaging records of patients undergoing 68Ga-FAPI PET/CT imaging in the Department of Nuclear Medicine of our hospital from March 2020 to March 2022 were retrospectively analyzed. Patients with benign lesions confirmed by histopathological analysis or long-term follow-up of FAPI-positive lesions were included in the study. RESULTS: A total of 44 patients (i.e., 44 benign lesions) were included in this study, including 14 women and 30 men, ranging in age from 19 to 74 years. Benign lesions involved eight systems, including liver (n = 3), tail of pancreas (n = 3), stomach (n = 3), esophagus (n = 1), lung (n = 14), and mediastinum (n = 2), sinuses (n = 1), brain (n = 2), lymph nodes (n = 5), kidneys (n = 4), bones (n = 2), muscles (n = 1), thyroid (n = 1), parathyroid gland (n = 1), and breast (n = 1). The mean SUVmax (p = 0.471) and mean TBR (p = 0.830) of benign lesions in the eight systems were not significantly different. CONCLUSION: Our studies have shown that in addition to malignant tumors, certain benign lesions also show uptake of FAPI, and it is necessary for doctors to distinguish these benign lesions from true malignant tumors. ADVANCES IN KNOWLEDGE: Benign lesions may also show FAPI expression, which may make the differential diagnosis of benign and malignant lesions difficult and should be alerted by physicians.

Similar Findings on 68 Ga-Pentixafor PET/CT and 18 F-FDG PET/CT in a Patient With Widespread Metastatic Hepatic Neuroendocrine Carcinoma.

ABSTRACT: A patient with suspected malignant tumor underwent 18 F-FDG PET/CT. Based on the findings, the patient was suspected of having multiple myeloma. Then the patient underwent 68 Ga-pentixafor PET/CT, which showed similar results to 18 F-FDG PET/CT. Finally, the patient was eventually diagnosed with neuroendocrine carcinoma.

Comparison of 18 F-MFBG and 68 Ga-DOTATATE PET/CT in the Imaging of Metastatic Paraganglioma and Pheochromocytoma.

ABSTRACT: Two men with metastatic paraganglioma/pheochromocytoma underwent PET/CT examination in our hospital to understand the treatment effect and progression of the disease. Both patients had previously been treated with 131 I-MIBG, and at this evaluation, both of them underwent 68 Ga-DOTATATE and 18 F-MFBG PET/CT. The 68 Ga-DOTATATE PET/CT showed more metastases in the images of these 2 patients. This case highlighted that 68 Ga-DOTATATE PET/CT is superior to 18 F-MFBG PET/CT in detecting metastases from paraganglioma and pheochromocytoma in these 2 patients.

Imaging Aldosterone-Producing Adrenocortical Carcinoma With 68 Ga-Pentixafor PET/CT.

ABSTRACT: Chemokine receptor 4 (CXCR4) is a 7-transmembrane G protein-coupled receptor, and pentixafor is considered to be a potent ligand for the CXCR4 receptor. Recently, 68 Ga-pentixafor has been reported as a potential PET imaging agent for CXCR4-positive tumors and inflammatory lesions, including adrenocortical lesions. We report a case of primary aldosteronism due to adrenocortical carcinoma with intense 68 Ga-pentixafor activity on PET/CT.

Intense 68 Ga-Pentixafor Activity in Idiopathic Retroperitoneal Fibrosis.

ABSTRACT: A 52-year-old man was admitted to our hospital with lower abdominal and low back pain, and abdomen CT at an outside hospital presented a retroperitoneal mass with left urinary tract obstruction and hydronephrosis. In 68 Ga-pentixafor PET/CT, the retroperitoneal mass showed intense radioactivity. Subsequently, the patient underwent biopsy of the retroperitoneal mass. The pathological examination showed only fibrous tissue without tumor cells. The patient was finally diagnosed with idiopathic retroperitoneal fibrosis. Our case demonstrated that idiopathic retroperitoneal fibrosis had intense uptake of 68 Ga-pentixafor.

Comparison of 68Ga-FAPI and 18F-FDG PET/CT in the Imaging of Pancreatic Cancer With Liver Metastases.

ABSTRACT: A 65-year-old man with suspected pancreatic cancer underwent 18F-FDG PET/CT for initial staging. Mild FDG uptake was observed in the pancreatic mass and bone destruction in the 10th rib on the right. No significant FDG uptake was seen with the multiple hypodense or isodense nodules in the liver. However, 68Ga-FAPI PET/CT revealed intense FAPI uptake in the pancreas and the 10th rib and multiple lesions in the liver. Finally, a biopsy confirmed carcinoma in the head of the pancreas with liver metastasis. This case highlighted that 68Ga-FAPI may outperform 18F-FDG PET/CT in identifying micrometastases of bones and hidden liver metastases.