Role of gallium-68-labeled FAPI-PET imaging in oncology: Results of a study in 310 patients.

Abstract

e15076 Background: Current oncological PET imaging approaches rely on metabolic targets, primarily 18 F-FDG, and this leads to diagnostic limitations in tumors with low proliferation, a predominant fibrotic stroma, or post-treatment changes. Fibroblast activation protein (FAP) is a widely expressed target in the tumor stroma, such as cancer-associated fibroblasts (CAFs), in numerous solid tumors. Gallium-68-labeled FAPI PET imaging is emerging as a novel, tumor-agnostic imaging paradigm that evaluates tumor biology at the stromal level. Methods: In our study, we performed 68 Ga-FAPI PET/CT and 18 F-FDG PET/CT imaging on 310 patients with different solid tumor diagnoses. The study population included lung, breast, gastrointestinal system, gynecological, genitourinary, hepatobiliary, thyroid, and rare solid tumors. Although multiple FAPI-PET examinations were performed in the same patient, the analysis was performed on a patient-by-patient basis. The images were evaluated by comparing FAPI uptake in primary and metastatic lesions with FDG. Results: A total of 310 patients underwent 68 Ga-FAPI PET/CT and 18 F-FDG PET imaging for comparison. Significant FAPI uptake was observed in the primary tumor and/or metastatic lesions in all cases, and in many cases, significant SUV values were present on FAPI-PET, which was more sensitive than FDG. Patient distribution was as follows: lung cancer (n = 33), breast cancer (n = 47), colorectal cancer (n = 47), gastric cancer (n = 29), pancreatic cancer (n = 17), hepatobiliary tumors (n = 8), prostate cancer (n = 8), gynecological tumors (n = 4), and thyroid cancer (n = 1). In addition, 116 patients had various rare solid tumor diagnoses. FAPI PET imaging demonstrated superior lesion detection performance by providing high tumor-background contrast with low physiological background activity in all tumor groups. Conclusions: This large patient series demonstrated that 68 Ga-FAPI PET imaging exhibits higher sensitivity than FDG-PET in solid tumors across the board. FAPI PET, which provides stromal-targeted imaging independent of tumor type, is a method that complements conventional metabolic imaging approaches and surpasses them in many clinical scenarios. Our findings strongly support the integration of 68 Ga-FAPI PET into clinical oncology imaging algorithms and guidelines. Distribution of tumor types in patients undergoing 68 Ga-FAPI PET/CT imaging. Tumor Type n Breast cancer 47 Colorectal cancer 47 Lung cancer 33 Gastric cancer 29 Pancreatic cancer 17 Hepatobiliary tumors 8 Prostate cancer 8 Gynecologic tumors 4 Thyroid cancer 1 Other solid tumors 116 Total 310 All patients underwent both 18 F-FDG PET/CT and 68 Ga-FAPI PET/CT imaging. Tumor types are reported on a per-patient basis. Visually significant tracer uptake was observed in all cases on 68 Ga-FAPI PET/CT.