68 Ga-FAPI-04 PET for Detecting Occult Peritoneal Metastasis in Locally Advanced Gastric Cancer: Diagnostic Performance and Cost Analyses in a Single-Center, Prospective Cohort Study

Occult peritoneal metastasis (OPM) is common in locally advanced gastric cancer, and accurate detection is critical. This prospective cohort study evaluated the diagnostic accuracy and cost of ⁶⁸Ga-FAPI-04 PET/CT for detecting OPM. Methods: This single-center, prospective cohort study included patients with locally advanced gastric adenocarcinoma. All patients underwent ⁶⁸Ga-FAPI-04 PET/CT before laparoscopic staging, and the diagnosis of OPM was established using laparoscopic staging combined with peritoneal washing cytology as the gold standard. The primary endpoint was the proportion of patients whose treatment intent changed based on ⁶⁸Ga-FAPI-04 PET/CT results. Secondary endpoints included diagnostic accuracy and cost analysis of ⁶⁸Ga-FAPI-04 PET/CT in detecting OPM. Results: In total, 109 patients were recruited between November 2022 and August 2024. ⁶⁸Ga-FAPI-04 PET/CT identified OPM in 17 patients (15.6%), resulting in upstaging to stage IV, with sensitivity, specificity, and diagnostic accuracy of 75.0%, 94.6%, and 91.7%, respectively (area under the curve, 0.83; 95% CI, 0.72–0.94). Economic analysis demonstrated a net cost savings of $979.30 per patient when compared with laparoscopic staging. The combination of ⁶⁸Ga-FAPI-04 PET/CT and laparoscopic staging reduced the need for laparoscopic procedures by 84% and prevented 11% of futile gastrectomies, yielding a minimal cost savings of $232.30 per patient. Conclusion: ⁶⁸Ga-FAPI-04 PET/CT demonstrates high diagnostic accuracy, low cost, and the potential to reduce invasive procedures, making it a promising alternative to laparoscopic staging in patients with locally advanced gastric cancer.