Initial Clinical Experience using 68Ga-FAPI-46 PET/CT for Detecting Various Cancer Types

Abstract Purpose Numerous studies have demonstrated that 68Ga-FAPI PET/CT scans would yield high intra-tumoral tracer uptake and low uptake in normal tissues as background, thus allowing for excellent visualization of lesions in the cancer microenvironment. This study set out to compare the suitability of 68Ga-FAPI-46 PET versus routine 18F-FDG PET, 68Ga-DOTATATE and 68Ga-Pentixafor radiotracers for the assessment of different types of cancer. Methods A retrospective analysis of 11 patients (6 males, 5 females; mean age: 53 years, range: 10–58 years) with histopathologically confirmed, well-differentiated adenocarcinoma, medullar thyroid cancer (MTC), papillary thyroid carcinoma (PTC), cervical, gastric, glioblastoma multiform (GBM), colon, Ewing's sarcoma, and breast cancer was performed. These patients underwent PET/CT scans using four different radiotracers (9 18F-FDG, 11 68Ga-FAPI, 3 68Ga-DOTATATE, and 1 68Ga-Pentixafor). The patients' PET/CT images were visually evaluated for cancer detection, and analyzed semi-quantitatively through image-derived metrics, such as target-to-background ratio (TBR) and maximum standard uptake value (SUVmax), for recurrence and metastasis. Results The study of 11 patients revealed that 68Ga-FAPI-46 was more effective than other tracers for detecting metastases, with 55 vs. 49 metastases in the lymph nodes, 4 vs. 3 in the liver, and 4 vs. 3 in the bones detected in comparison to 18F-FDG. No significant differences were observed in 68Ga-DOTATATE and 68Ga-Pentixafor PET images (P-value > 0.05). In addition, in five patients, the SUVmax and TBR values​​ in 68Ga-FAPI-46 PET images were significantly higher than 18F-FDG PET images for lymph nodes and bone metastases. Although the SUVmax in 68Ga-FAPI-46 and 18F-FDG PET images for liver metastases was comparable, 68Ga-FAPI-46 had a significantly higher TBR than 18F-FDG. Conclusions 68Ga-FAPI-46 PET images led to improved detection rates for most metastases and better patient classification compared to 18F-FDG, 68Ga-Pentixafor, and 68Ga-DOTATATE. However, 18F-FDG PET/CT detected more lymph nodes than 68Ga-FAPI-46 PET/CT in various types of cancer.