The Role of 68Ga-FAPI PET/CT in Detection of Metastatic Lobular Breast cancer.

PURPOSE: Invasive lobular breast cancer (ILC) may be hard to detect using conventional imaging modalities and usually shows less avidity to 18F-FDG PET/CT. 68Ga-fibroblast activation protein inhibitor (FAPI) PET/CT has shown promising results in detecting non-18F-FDG-avid cancers. We aimed to assess the feasibility of detecting metastatic disease in patients with non-18F-FDG-avid ILC.

METHODS: This prospective study included patients with metastatic ILC, infiltrative to soft tissues, which was not 18F-FDG avid. The patients underwent 68Ga-FAPI PET/CT for evaluation, which was correlated with the fully diagnostic CT performed at the same time.

RESULTS: Seven women (aged 57 ± 10 years) were included. Among the 30 organs and structures found to be involved by tumor, the number of findings observed by FAPI PET/CT was significantly higher than that observed by CT alone (P = 0.022), especially in infiltrative soft tissue and serosal locations.

CONCLUSIONS: This small pilot trial suggests a role for 68Ga-FAPI PET/CT in ILC, which needs to be confirmed by subsequent trials.