Analysis and Outlook on the Use of 99mTc-FAPI SPECT/CT in the Diagnosis of Primary and Metastatic Lesions of Cholangiocarcinoma.

Abstract

Introduction: Cholangiocarcinoma (CCA) is an aggressive malignancy characterized by a poor prognosis, where timely diagnosis and accurate staging are critical yet challenging. Conventional imaging techniques often fail to effectively differentiate primary lesions from micrometastases or to distinguish benign from malignant findings. Fibroblast activation protein (FAP), highly expressed in cancer-associated fibroblasts, presents a promising molecular target for improving diagnostic precision.

Materials and methods: This review synthesizes current clinical evidence regarding the application of technetium-99m-labeled FAP inhibitors (^99mTc-FAPI) in single-photon emission computed tomography/computed tomography (SPECT/CT) for the detection of primary and metastatic cholangiocarcinoma. The analysis focuses on the diagnostic performance, sensitivity, and clinical utility of ^99mTc-FAPI SPECT/CT compared to standard imaging modalities such as contrast-enhanced CT and ¹⁸F-FDG PET/CT.

Results: Literature indicates that FAP is expressed in over 93% of cholangiocarcinoma stroma, providing a strong rationale for FAPI imaging. Clinical studies demonstrate that ^99mTc-FAPI SPECT/CT effectively detects primary lesions with performance comparable to ¹⁸F-FDG PET/CT. Notably, it exhibits superior sensitivity for identifying lymph node and peritoneal metastases compared to contrast-enhanced CT, detecting a higher number of lesions.

Conclusions: ^99mTc-FAPI SPECT/CT holds significant potential as a valuable tool for the diagnosis and staging of cholangiocarcinoma, serving as an effective complement to existing imaging methods. Despite challenges such as lower spatial resolution and the need for standardized protocols, the modality offers economic and logistical advantages. Further well-designed, large-scale studies are required to validate these findings and support broader clinical adoption.