Comparison of diagnostic performance of [68Ga]-Ga-FAPI-46 and [18F]-FDG PET/CT imaging for the detection of lesions and disease staging in patients with breast cancer.

Abstract

Objectives: To compare the diagnostic performance of [⁶⁸Ga]-Ga-FAPI-46 and [¹⁸F]-FDG PET/CT imaging for the detection of lesions and disease staging in breast cancer.

Methods: Twelve female patients with breast cancer (mean age= 49.2±13.29 years) and previous [¹⁸F]-FDG PET/CT were recruited in the study. [⁶⁸Ga]Ga-FAPI-46 imaging performed in all patients within one month after [¹⁸F]-FDG PET/CT imaging. The acquired PET/CT data with both tracers were reconstructed. Tracer avid lesions with each PET tracer were identified and the semi-quantitative parameters i.e. SUV_max, lesion counts and target-to-background ratio (TBR_max) were analyzed.

Results: Physiologic distribution of [⁶⁸Ga]-Ga-FAPI-46 was observed in the liver, blood pool and kidneys, whereas no tracer uptake was noted in the brain and heart. The mean liver SUV_max for [⁶⁸Ga] Ga-FAPI-46 was 1.5±0.1 which was lower than that noted for [¹⁸F]-FDG PET/CT (2.9±0.2). Likewise, the mean blood pool SUV_max value for [⁶⁸Ga]-Ga-FAPI-46 was lower than [¹⁸F]-FDG PET/CT (1.7±0.1 versus 2.0±0.1). [⁶⁸Ga]-Ga-FAPI-46 PET/CT demonstrated higher tracer uptake in the lesions detected in the brain, bone, internal mammary and lymph nodes in 4/12 patients. The overall lesions detections and the mean SUV_max values did not differ significantly between the two techniques. On the other hand, [⁶⁸Ga]-Ga-FAPI-46 demonstrated higher mean TBR_max than [¹⁸F] FDG PET/CT particularly for lesions detected in kidneys, chest wall, mediastinum, and musculoskeletal lesions. However, both techniques offered identical TNM staging.

Conclusion: The findings of this preliminary study demonstrated that [⁶⁸Ga]-Ga-FAPI-46 and [¹⁸F]-FDG PET/CT offered identical disease staging in the breast cancer patients. [⁶⁸Ga]-Ga-FAPI-46 showed lower liver and blood pool uptake and an enhanced tumor-to-background ratio, thereby suggesting its potential for improved lesions detection. This may open opportunity for emerging FAP based radioligand for therapeutic applications in advanced stage breast cancers. However, this needs validation in a larger number of patients.