The Role of FAPI PET/CT in Exploring the Microenvironment of Colorectal Cancer Liver Metastases: Non-randomized Phase II Molecular Imaging Study

The tumor microenvironment (TME) plays an important role in tumor development and therapeutic response. The understanding of the TME components, especially cancer-associated fibroblasts (CAFs) remains limited. CAFs are among the most abundant and versatile components of the tumor stroma and they are implicated in all the hallmarks of cancer. They have a heterogenous phenotype within a single cell. Some CAFs may have immunosuppressive properties. In liver, there are two obvious physiological sources of CAFs: resident portal fibroblasts (PFs) and hepatic stellate cells (HSCs) . A recent study showed that based on the gene expression profile there are three major subsets of CAFs in colorectal primary tumors and in liver metastasis, including secretory CAFs, ECM-remodeling CAFs and contractile CAFs . In patients undergoing resection of colorectal liver metastasis (CRLMs) the histological growth patterns (HGP) reflect tumor biology and local infiltrating behavior . The HGPs of liver metastases reflect the ways in which cancer cells interact with the surrounding liver. The transition from one HGP to another could occur in patients with CRLM following systemic treatment .

FAPI PET/CT molecular imaging represents a cutting-edge advancement in oncological imaging, particularly for the preoperative assessment of colorectal liver metastases (CRLM). Fibroblast activation protein inhibitors (FAPIs), which are the focus of this imaging modality, selectively target cancer-associated fibroblasts, a critical component of the tumor microenvironment. FAPI PET/CT could be useful in the detection of HGP and in the changes during neoadjuvant chemotherapy prior to surgery