Epithelial ovarian cancer (EOC) is a tumor entity featured by frequent involvement of peritoneum, also called peritoneal carcinomatosis. It is a type of metastasis accompanied by significant cancer-associated fibroblasts (CAFs) accumulation. Fibroblast activation protein (FAP) is a protein that is overexpressed on CAFs and can be non-invasively monitored by a novel radiotracer called 68Ga-FAPI-04 positron emission tomography/computed tomography (PET/CT). In this study, we will explore the value of 68Ga-FAPI-04 PET/CT in patients with epithelial ovarian cancer who are scheduled for surgical intervention. The findings of 68Ga-FAPI-04 PET/CT will also be compared with that of 18F-2-fluoro-2-deoxy-D-glucose fluorodeoxyglucose (18F-FDG) PET/CT, which is one of the most commonly used modalities in evaluating EOC, and histological findings.

Patients with epithelial ovarian cancer who are scheduled for surgical intervention will be recruited in this study. They will undergo a comparative 68Ga-FAPI-04 and 18F-FDG PET/CT study before the surgery. No tumor-specific treatment is allowed between the scan and surgery, e.g. adjuvant chemotherapy, neoadjuvant chemotherapy, and intraperitoneal chemotherapy. Three types of lesions will be marked based on 68Ga-FAPI-04 and 18F-FDG PET/CT findings, which is FAPI+/FDG-, FAPI-/FAPI+, and FAPI+/FDG+ lesions. The marked lesions will be explored by the surgeon, resected if possible, and compared with histological results. A fourth type of lesion will be added into the analysis if that lesion is both FAPI and FAP negative but is a histological-confirmed positive lesion.

Inclusion Criteria:

• Written informed consent signed
• EOC patients who are scheduled for surgery. The diagnosis of EOC should be based on the previous histological results or cytological evaluation combined with a serum CA-125 to carcinoembryonic antigen ratio>25 to confirm the primary diagnosis and exclude a nongynecologic cancer.

Exclusion Criteria:

• Known hypersensitivity to any of the excipients of 18F-FDG and 68Ga-FAPI-04.
• Tumor-specific treatment is necessary between the scans and surgery, e.g. adjuvant chemotherapy, neoadjuvant chemotherapy, and intraperitoneal chemotherapy.
• Pregnant or breast-feeding women.
• Any mental condition rendering the patient unable to understand the nature, scope, and possible consequences of the study, and/or evidence of an uncooperative attitude.

Ovarian cancer is a female-specific tumor entity.