A 68-year-old woman with a mass lesion in right hepatic lobe had an elevated α-fetoprotein level (>54,000 ng/mL). The lesion showed higher 68 Ga-DOTA-FAPI-04 uptake than 18 F-FDG uptake in consecutive PET/CT images. The histopathological examination revealed neuroendocrine carcinoma with Ki-67 proliferation index of 80%.

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Aim Aim of study is to compare the results of Gallium-68-prostate-specific membrane antigen ( 68 Ga-PSMA) and 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography(PET)/computed tomography (CT), to evaluate the correlation between PET findings and the level of PSMA, Claudin (Clau) 1, 4, and 7 receptors obtained by immunohistochemical (IHC) analysis, and to determine potential predictive and prognostic values in TNBC.Methods Forty-seven lesions of 42 subjects diagnosed TNBC both underwent PET/CT scan for preoperative staging/restaging were prospectively included study. PSMA, Clau 1, 4, and 7 expressions were IHC evaluated from the biopsy samples of the primary tumor (PT). Maximum standardized uptake value(SUV max) of the PT, lymph node, and distant organ metastases (DOMs) on 18 F-FDG and 68 Ga-PSMA PET/CT were compared with PSMA, Clau 1, 4, and 7 receptor expressions.Results IHC analyses on 29 BC lesions to demonstrate Clau expression showed 86% (25/29) Clau 1, 86% (25/29) Clau 4, 45% (13/29) Clau 7, and 48% (14/29) PSMA-positive. The mean DOM (SUVmax) was 15.5 ± 11.6 for 18 F-FDG and 6.0 ± 2.9 for 68 Ga-PSMA. Axial diameter of BC PT had a significant positive correlation with 18 F-FDG SUVmax, 68 Ga-PSMA SUVmax, and PSMA scores. BC lesions 68 Ga-PSMA SUVmax had a significant negative correlation with the Ki-67 index. Axial diameter of the primary tumor had significant negative correlation with Clau 7 scores (r = −0.409, P = 0.034). Absence of Clau 1 expression found to significantly increase the rate of DOM (100% vs. 28%) (P = 0.014). All patients with axillary lymph node (ALN) metastases (n = 17, 100%) exhibited Clau 4 positivity (P = 0.021). The presence of PSMA expression observed to significantly increase the rate of ALN metastases (64.7% vs. 25%) (P = 0.035). ConclusionConfirming PSMA expression with PET imaging would be significant as PSMA, a theranostic agent, may be a considerable potential agent for radionuclide treatment strategies, in addition to its additional diagnostic contribution to FDG, especially in patients with metastatic TNBC, which is an aggressive, heterogeneous disease.

PurposeIn this prospective study, PET findings of 18F-FDG PET/CT in breast cancer staging were compared with 68Ga–FAP inhibitor (FAPI) 04 PET/CT findings in selected cases with relatively low 18F-FDG uptake in the primary tumor or with suspected nodal or distant metastases.Patients and MethodsTwenty-four women with a median age of 45 years (range, 36–67 years) who underwent initial staging 18F-FDG PET/CT for breast cancer underwent 68Ga-FAPI-04 PET/CT imaging within the same week. SUVmax and quantities of primary tumors and locoregional and distant metastatic lesions were recorded from both images, and these data were compared statistically.ResultsThe histological subtypes of primary tumors were 11 invasive lobular, 8 invasive ductal, and 5 mucinous subtypes. More intense 68Ga-FAPI-04 uptake (mean, 17.1 ± 7.9; 7.4–38.5) was detected in all primary tumoral lesions compared with 18F-FDG (mean, 6.3 ± 3.9; 1.5–20.5) (P = <0.001, Z = 4.107). Additional lesions showing 68Ga-FAPI-04 uptake in the breast were detected in 29.2% (n = 7) of patients. In 8.3% (n = 2) of the patients, the primary lesion showed only 68Ga-FAPI-04 uptake. In 68Ga-FAPI-04 PET/CT, 25% (n = 6) of the patients showed more lymph node involvement and more intense uptake in the ipsilateral axilla. In addition, infraclavicular (level 3) lymph nodes in 4 patients (16.7%), supraclavicular lymph nodes in 1 patient, and internal mammary lymph nodes in 1 patient were detected only on 68Ga-FAPI-04 PET/CT. In a patient with lung and bone metastases, 68Ga-FAPI-04 uptake was higher, and the lung nodule showed only 68Ga-FAPI-04 uptake.ConclusionsIn selected low-FDG-affinity breast cancer patients, 68Ga-FAPI-04 PET/CT showed the primary tumor with higher sensitivity and higher SUVmax values compared with 18F-FDG PET/CT. In addition, it is believed that this method may contribute to the management of patients' treatment by increasing the nodal stage.

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