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

Abstract

PurposeInvasive 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.MethodsThis 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.ResultsSeven 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.ConclusionsThis small pilot trial suggests a role for 68Ga-FAPI PET/CT in ILC, which needs to be confirmed by subsequent trials.

The Role of 68Ga-FAPI PET/CT in Breast Cancer Response Assessment and Follow-Up

“…The study cohort included patients with metastatic ILC, with non–FDG-avid PET/CT scans who had baseline 68 Ga-FAPI–avid PET/CT scans as described in a previous study, 4 and continued to undergo FAPI imaging as part of their clinical follow-up. Exclusion criteria included patients who refused or were noneligible for follow-up scans (Fig.…”

“…Recent studies show that 68 Ga-labeled fibroblast activation protein inhibitor ( 68 Ga-FAPI), a new PET/CT radiotracer targeting cancer-associated fibroblasts in the tumor microenvironment, can be used in disease detection, as many tumors depend on activated fibroblasts to sustain viability and growth 1–3 . This also includes invasive lobular breast cancer (ILC), which is difficult to detect and follow on CT or FDG PET/CT because of an infiltrative spread pattern and low avidity to FDG 4–7 …”

“…[1][2][3] This also includes invasive lobular breast cancer (ILC), which is difficult to detect and follow on CT or FDG PET/CT because of an infiltrative spread pattern and low avidity to FDG. [4][5][6][7] Tracers such as FDG, which reflects tumor metabolism, and prostate-specific membrane antigen, which represents membrane peptide expression, can be used to detect disease progression and assess response to treatment, as they correlate well with cancer cell burden or function. [8][9][10][11] As cancer cells grow, they activate cancer-associated fibroblasts in the microenvironment, building their infrastructure and interacting with growth factors and cytokines 3 ; therefore, it stands to reason that 68 Ga-FAPI can also detect tumor growth.…”

FAPI PET/CT Imaging—An Updated Review

“…However, [ 18 F]AlF-FAPI-74 was reported to have lower specificity activity when compared to its 68 Ga-labeled counterpart, which could potentially affect image quality [34]. Novel tracers have also been developed for single photon emission computed tomography (SPECT) imaging such as 99m Tc-labeled FAPI-34, 99m Tc-labeled FAP-targeting ligand (FL-L3), and 111 In-labeled QCP02. In addition to 177 Lu, FAPI molecules have also been radiolabeled with 188 Re, 90 Y, and 225 Ac for therapeutic application [35][36][37][38][39].…”

Clinical applications of fibroblast activation protein‐targeted theranostics in oncologic and nononcologic disease: Current status and future directions

“…Subsequently, a series of studies demonstrated that the TBR derived from 68 Ga‐FAPI PET can classify pathological response correctly after neoadjuvant chemotherapy for breast cancer [97, 98]. In addition, FAPI PET/CT could possibly be used for disease response assessment and follow‐up based on the strong correlation between cancer progression and regression and FAPI‐based tumor volume [99, 100].…”