⁶⁸Ga-FAPI-04 positron emission tomography/CT and laparoscopy for the diagnosis of occult peritoneal metastasis in newly diagnosed locally advanced gastric cancer: study protocol of a single-centre prospective cohort study.

Abstract

Accurate baseline clinical staging is critical to inform treatment decision-making for patients with gastric cancers. Peritoneal metastasis (PM) is the most common form of metastasis in gastric cancer and mainly diagnosed by diagnostic laparoscopy and peritoneal lavage evaluation. However, diagnostic laparoscopy is invasive and less cost-effective. It is urgent to develop a safe, fast and non-invasive functional imaging method to verify the peritoneal metastasis of gastric cancer. The aim of our study was to evaluate the proportion of patients in whom ⁶⁸Ga-FAPI-04 positron emission tomography/CT (PET/CT) led to a change in treatment strategy and to assess the diagnostic accuracy of ⁶⁸Ga-FAPI-04 PET/CT for the detection of occult peritoneal metastasis compared with laparoscopic exploration. In this single-centre, prospective diagnostic test accuracy study, a total of 48 patients with locally advanced gastric or gastro-oesophageal junction adenocarcinoma (cT4a-b, N0-3, M0, based on CT images) who are considering radical tumour surgery will be recruited. All participants will undergo ⁶⁸Ga-FAPI-04 PET/CT before the initiation of laparoscopic exploration. The primary outcome is the proportion of patients with occult peritoneal metastatic lesions detected by ⁶⁸Ga-FAPI-04 PET/CT, leading to a change in therapy strategy. The secondary outcomes include the diagnostic performance of ⁶⁸Ga-FAPI-04 PET/CT for occult peritoneal metastasis, including sensitivity, specificity, accuracy, positive predictive value and negative predictive value. The study protocol was approved by the Ethics Committee of West China Hospital, Sichuan University (2022-1484). Study results will be presented at public and scientific conferences and in peer-reviewed journals. ChiCTR2300067591.