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

Purpose Numerous studies have demonstrated that 68 Ga-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 68 Ga-FAPI-46 PET versus routine 18 F-FDG PET, 68 Ga-DOTATATE and 68 Ga-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 18 F-FDG, 11 68 Ga-FAPI, 3 68 Ga-DOTATATE, and 1 68 Ga-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 (SUV max ), for recurrence and metastasis. Results The study of 11 patients revealed that 68 Ga-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 18 F-FDG. No significant differences were observed in 68 Ga-DOTATATE and 68 Ga-Pentixafor PET images (P-value > 0.05). In addition, in five patients, the SUV max and TBR values​​ in 68 Ga-FAPI-46 PET images were significantly higher than 18 F-FDG PET images for lymph nodes and bone metastases. Although the SUV max in 68 Ga-FAPI-46 and 18 F-FDG PET images for liver metastases was comparable, 68 Ga-FAPI-46 had a significantly higher TBR than 18 F-FDG. Conclusions 68 Ga-FAPI-46 PET images led to improved detection rates for most metastases and better patient classification compared to 18 F-FDG, 68 Ga-Pentixafor, and 68 Ga-DOTATATE. However, 18 F-FDG PET/CT detected more lymph nodes than 68 Ga-FAPI-46 PET/CT in various types of cancer.