⁶⁸Ga-FAPI-04 positron emission tomography/computed tomography (PET/CT) for detecting occult peritoneal metastasis in locally advanced gastric cancer: A single-center prospective cohort study.

61 Background: Occult peritoneal metastasis (OPM) is a common finding in patients diagnosed with advanced gastric cancer. Preoperative diagnosis of OPM is crucial for developing treatment strategies and for evaluating the prognosis of patients with locally advanced gastric cancer. To evaluate the accuracy of 68 Ga-FAPI-04 PET/CT in diagnosing OPM in locally advanced gastric cancer. Methods: This was a prospective, observational, single-center, single-blind, cohort study. Patients with histologically proven locally advanced gastric or gastroesophageal junction adenocarcinoma on initial staging evaluation were recruited. Laparoscopic staging and cytological analysis of peritoneal washing served as reference standards for the final diagnosis. The primary outcome was the proportion of participants changing treatment strategy from curative to palliative treatment. Results: A total of 49 patients were recruited between November 2022 and July 2023 . Nine of the 49 patients were diagnosed with OPM following 68 Ga-FAPI-04 PET/CT examinations. A total of 18.4% (n=9) of patients with locally advanced disease on initial staging evaluation by contrast-enhanced CT were upstaged to stage IV for peritoneal metastasis on 68 Ga-FAPI-04 PET/CT. The sensitivity of 68 Ga-FAPI-04 PET/CT in detecting OPM was 85.7%, and the specificity was 92.3%. The overall diagnostic accuracy of 68 Ga-FAPI-04 PET/CT was 91.8%. Based on ROC curve analysis, the area under the curve (AUC) was 0.893 (95% CI: 0.734–1). Conclusions: The findings of this study suggest a significantly additional value of 68 Ga-FAPI-04 PET/CT in detecting OPM. Thus, it would be useful to include 68 Ga-FAPI-04 PET/CT in the guidelines for staging locally advanced gastric cancer, instead of laparoscopic staging. Clinical trial information: ChiCTR2300067591 .