Breast cancer is a complex, heterogeneous disease comprising numerous distinct biological subtypes characterized by variant pathobiological features and clinical behaviors. 18F-fluorodeoxyglucose (18F-FDG) PET/CT, an essential imaging modality in the characterization of metabolism within the tumor, has successfully evolved in the diagnosis, staging, and assessment of treatment response in patients with breast cancer. Cancer-associated fibroblasts (CAFs) are a crucial component of the tumor stroma with diverse functions. Fibroblast activation protein (FAP), a type II membrane-bound glycoprotein from the dipeptidyl peptidase-4 family, is highly expressed in the CAFs of several epithelial carcinomas, including breast cancer, coupled with relatively low expression in normal tissue. Gallium-68 (68Ga)-conjugated FAP inhibitor (FAPI), a new radiotracer targeting FAP, has been developed for targeting FAP and tumor-stromal visualization. With its fast renal clearance and high tumor-to-background ratio, 68Ga-FAPI has been successfully validated in multi-types of tumors. This study aims to evaluate the performance and value of 68Ga- FAPI PET/CT in patients with breast cancer.
