Ga68-FAPI-46 PET/CT for Preoperative Assessment of Peritoneal Carcinomatosis (FAPeCa)

Ga68-labeled Fibroblast Activation Protein Inhibitor-46 (Ga68-FAPI-46) PET/CT for Preoperative Assessment of Peritoneal Carcinomatosis

This is a prospective, phase II, non-randomized clinical imaging trial. Ga68-FAPI-46 is a novel radiotracer used in PET/CT imaging, targeting a protein of the tumor microenvironment called FAP (Fibroblast activation protein). The aim of the study is to assess the accuracy of Ga68-FAPI-46 PET/CT for preoperative assessment of peritoneal carcinomatosis in colorectal and ovarian cancer.

Fibroblast activation protein (FAP) is a type II transmembrane glycoprotein expressed on the surface of cancer-associated fibroblasts (CAFs) in the stroma of various tumor entities. Recently, radiolabeled molecules targeting the FAP, called FAP inhibitors (FAPI) labelled with Gallium-68, have been developed for molecular imaging with PET/CT (positron emission tomography/computed tomography). This radiotracer often presents a higher cancer lesion detectability than F18-FDG (fluorodeoxyglucose), partly thanks to its higher tumour-to-background ratio achieved by a low background activity, particularly in the brain, abdominal cavity and liver. These advantages have resulted in a superior sensitivity of Ga68-FAPI PET/CT over F18-FDG and higher SUV (standardized uptake value) in evaluating various types of cancer. In this context, Ga68-FAPI PET/CT seems promising to further study as a clinical imaging modality for preoperative assessment of peritoneal carcinomatosis. In this study, the investigators correlate Ga68-FAPI PET/CT findings in terms of peritoneal involvement with intraoperative findings based on histopathology and try to find out how accurate Ga68-FAPI PET/CT is for the preoperative assessment of peritoneal carcinomatosis.

colorectal cancer, ovarian cancer, peritoneal carcinomatosis, fibroblast activation protein inhibitor, positron emission tomography, FAPI-46, PET, FAPI, PET/CT, fibroblast activation protein

Patients with known or suspected peritoneal metastases from colorectal and ovarian cancers scheduled for complete cytoreductive surgery undergo FAPI PET/CT before the planned surgery. In the target population, patients receiving neoadjuvant chemotherapy undergo FAPI PET/CT both before and after chemotherapy.

The radiopharmaceutical 68Gallium-FAPI-46 (FAPI) is applied intravenously for molecular imaging of FAP expression with FAPI PET/CT.

Correlation of the Ga68-FAPI PET/CT derived PCI (peritoneal cancer index) score with the intraoperative PCI based on histopathology of resected specimen (the reference standard)

Intraoperative PCI validated by histopathology performed on resected peritoneal metastases obtained during peritoneal cytoreductive surgery/explorative laparoscopy or laparotomy will be correlated with Ga68-FAPI PET/CT derived PCI.

Through completion of post-surgical pathological examination, up to 2 years since the study initiation

Comparison of PCI obtained with Ga68-FAPI PET/CT to the PCI calculated on standard preoperative imaging.

PCI calculated on standard preoperative imaging (MRI and FDG PET/CT) will be correlated with Ga68-FAPI PET/CT derived PCI.

Assessment of the impact of neoadjuvant chemotherapy on the FAPI expression of target lesions at baseline.

Subgroup: Patients receiving neoadjuvant chemotherapy Treatment-induced change in the total peritoneal tumor volume and uptake intensity of FAPI on PET/CT will be assessed and correlated to histopathological findings.

Through completion of post-neoadjuvant chemotherapy FAPI PET examination,up to 2 years since the study initiation

Inclusion Criteria: Histologically proven colorectal and ovarian cancer. Known or suspected peritoneal metastases from the tumour of origin. Scheduled for peritoneal complete cytoreductive surgery with curative intent with or without neoadjuvant chemotherapy. ECOG (Eastern Cooperative Oncology Group) Performance status ≤2. Signed written informed consent obtained before any study-specific screening procedures. Exclusion Criteria: Non-resectable extra-abdominal metastasis and/or >3 hepatic metastases on standard work-up Known chronic inflammatory conditions including the intestinal system (eg. inflammatory bowel disease, Crohn's disease) Pregnant and lactating women Previous or concurrent malignancy diagnosed within the last 3 years except adequately treated in situ carcinoma of the cervix uteri and basal or squamous cell skin cancer. Subjects with another significant medical condition which, in the investigator's opinion, may interfere with the completion of the study.