Tumor Imaging With 68Ga-DOTA-FAPI-04 PET/CT Comparison With 18F-FDG PET/CT in 22 Different Cancer Types

Introduction and Aim Cancer-associated fibroblasts, which are densely found in tumor tissue, express high levels of fibroblast activation protein (FAP), and FAP inhibitors (FAPIs) labeled with radionuclides can be used in the diagnosis and treatment of cancer. In this study, the role of Ga-68-DOTA-FAPI-04 PET/CT in imaging of primary, metastatic, and recurrent cancers was investigated. Patients and Methods A total of 42 patients (16 females, 26 males; mean age, 58.5 years; range, 31-84 years) with 22 different types of malignant diseases were included in the study. Ga-68-DOTA-FAPI-04 PET/CT imaging was performed 1 to 7 days after F-18-FDG PET/CT. Pathological uptake levels in primary tumoral lesions, lymph nodes, skeletal system, liver, peritoneal surfaces, and other body parts were compared between 2 PET/CTs. In addition, physiological uptake levels of F-18-FDG and Ga-68-FAPI were defined measuring the liver, thoracic aorta, gluteal muscle activities, and uterus activity in female patients. Results Of the 42 patients in the study group, 33 patients were included for staging, 8 patients for restaging, and 1 patient for evaluation of treatment response. Ga-68-DOTA-FAPI-04 PET/CT showed intense uptake in 94.2% of primary tumoral lesions. In patients with multiple myeloma, F-18-FDG uptake in the bone marrow was significantly higher than Ga-68-FAPI uptake, whereas in gastric signet ring cell tumors, Ga-68-FAPI uptake was found to be significantly higher than F-18-FDG uptake. It was observed that Ga-68-DOTA-FAPI-04 PET/CT detected bone, liver, and peritoneum metastases with higher sensitivity and accuracy compared F-18-FDG PET/CT. Conclusions The preliminary findings of this study showed that Ga-68-DOTA-FAPI-04 PET/CT can contribute to the diagnostic process in solid tumors. Especially in malignancies with mild uptake on F-18-FDG PET/CT, it stands out in diagnosis, staging, and restaging. It is also predicted that FAPI molecules can be used for radionuclide therapy in patients with metastatic disease and unresponsive to other treatments showing intense uptake on Ga-68-DOTA-FAPI-04 PET/CT.