Role of [68Ga]Ga-DOTA-FAPI-04 PET/CT in the evaluation of peritoneal carcinomatosis and comparison with [18F]-FDG PET/CT

Purpose The aim of this study was to explore the role of [Ga-68]Ga-DOTA-FAPI-04 positron emission tomography/computed tomography (PET/CT), compared with F-18-fluorodeoxyglucose [F-18]-FDG PET/CT, for evaluating peritoneal carcinomatosis in patients with various types of cancer. Methods Patients with suspected peritoneal malignancy, who underwent both [F-18]-FDG and [Ga-68]Ga-DOTA-FAPI-04 PET/CT between October 2019 and August 2020, were retrospectively analysed. The radiotracer uptake, peritoneal cancer index (PCI) score, and diagnostic performance of [F-18]-FDG and [Ga-68]Ga-DOTA-FAPI-04 PET/CT were evaluated and compared. Results Our cohort consisted of 46 patients, including 16 patients with diffuse-type peritoneal carcinomatosis, 27 with nodular-type peritoneal carcinomatosis, and 3 true-negative patients. A significant difference in standard uptake values (SUV) of lesions between [F-18]-FDG and [Ga-68]Ga-DOTA-FAPI-04 PET/CT examination was observed (median SUV: 3.48 vs. 9.82; P < 0.001), particularly in peritoneal carcinomatosis from gastric cancer (median SUV: 3.44 vs. 8.05; P = 0.001). Moreover, [Ga-68]Ga-DOTA-FAPI-04 PET/CT showed a higher PCI score and better sensitivity than [F-18]-FDG PET/CT for the detection of peritoneal carcinomatosis (6 vs. 18; P < 0.001; 72.09% vs. 97.67%; P = 0.002). Conclusion [Ga-68]Ga-DOTA-FAPI-04 PET/CT demonstrated superior sensitivity over [F-18]-FDG PET/CT for the detection of peritoneal carcinomatosis in patients with various types of cancer, particularly gastric cancer. Furthermore, the uptake of [Ga-68]Ga-DOTA-FAPI-04 in peritoneal carcinomatosis was significantly higher than that of [F-18]-FDG, demonstrating a larger extent of the lesions and yielding a higher PCI score. This could help enhance the image contrast, improve physicians' diagnostic confidence, and reduce the proportion of missed diagnoses.