68Ga-FAPI-04 PET/CT in Selected Breast Cancer Patients With Low FDG Affinity

Abstract

PurposeIn this prospective study, PET findings of18F-FDG PET/CT in breast cancer staging were compared with68Ga–FAP inhibitor (FAPI) 04 PET/CT findings in selected cases with relatively low18F-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 staging18F-FDG PET/CT for breast cancer underwent68Ga-FAPI-04 PET/CT imaging within the same week. SUVmaxand 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 intense68Ga-FAPI-04 uptake (mean, 17.1 ± 7.9; 7.4–38.5) was detected in all primary tumoral lesions compared with18F-FDG (mean, 6.3 ± 3.9; 1.5–20.5) (P= <0.001,Z= 4.107). Additional lesions showing68Ga-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 only68Ga-FAPI-04 uptake. In68Ga-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 on68Ga-FAPI-04 PET/CT. In a patient with lung and bone metastases,68Ga-FAPI-04 uptake was higher, and the lung nodule showed only68Ga-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 SUVmaxvalues compared with18F-FDG PET/CT. In addition, it is believed that this method may contribute to the management of patients' treatment by increasing the nodal stage.