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Advances in Radiotherapy
& Nuclear Medicine Diagnostics gude of biliary tract cancer

2.4. Invasive techniques 94% in patients with CCA, although it has a significantly

Endoscopic diagnosis is essential for most patients with higher detection rate for distal tumors (100%) compared
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CCA. 76,77 The diagnostic performance of these methods to proximal tumors (83%). Tissue sampling from
depends on the tumor’s location, as well as the knowledge extrahepatic localized primary tumors using EUS is
and experience of the endoscopist. ERCP and EUS typically reserved for inoperable or metastatic CCAs,
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remain the most commonly used endoscopic diagnostic particularly for distal stenosis or mass CCAs. EUS-
tools. However, endoscopy should be preceded by guided biopsy of tumors or lymph nodes is a highly
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an evaluation of disease severity using cross-sectional sensitive diagnostic method. In a study of 263 patients,
imaging, as cholangitis requiring immediate drainage the accuracy of EUS-guided fine-needle aspiration (EUS-
occurs in only 10% of patients at the time of their initial FNA) compared with ERC-based tissue sampling was
presentation. Other technologies, such as fluorescence 76.1% versus 60.5%, with diagnostic sensitivities of 73.6%
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in situ hybridization, single-slice cholangioscopy, confocal for EUS-FNA and 56.5% for ERC. Onda et al. suggest
laser endomicroscopy, and intraductal ultrasound, are also that EUS-FNA could be used as a first-line diagnostic
increasingly being utilized. 76 method, although its exact usefulness remains to be fully
verified. EUS can assess the status of regional lymph nodes
Direct ERC is critical in the evaluation and treatment and the local extent of eCCA. Although ERC, with or
of CCA and often serves as an essential diagnostic tool. 79,80 without brushing and biopsy, remains the primary choice
This procedure determines the anatomy of the biliary tract, for diagnosing CCA, EUS-FNA plays an important role in
enables biopsy collection from the lesion or lancet smear clinical practice. EUS-FNA can be performed not only to
for cytological evaluation, and functions therapeutically collect tissue samples from tumors but also from enlarged
in biliary stricture dilation and stenting. 79,80 However, ERC lymph nodes. The method provides slightly better
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cannot determine the full extent of the tumor. Detection results than ERCP in diagnosing biliary tract cancer.
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of a dominant stricture, with or without accompanying The information from EUS can be used to guide patient
proximal bile duct dilation or the presence of a polypoid care and improve outcomes, though it can also be used in
lesion, indicates the presence of pCCA. These findings ways that compromise patient well-being. A study by De
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should prompt further cytologic evaluation using bile Jong et al. demonstrated that EUS with tissue harvesting
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duct brushing. Tissue collection through brush cytology can be useful in patients with potentially resectable pCCA
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and tick biopsy allows for cytological and/or histological based on pre-operative cross-sectional imaging, regardless
confirmation of the disease. Conventional cytology of lymph node enlargement. A modification of ultrasound
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obtained through ERCP is suboptimal due to limited technology allows for the placement of an intraductal high-
sensitivity, though it remains the gold standard with high frequency ultrasound (IDUS) probe. Although certain
specificity. ERC is particularly useful for determining features, such as irregular wall thickening, may strongly
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tumor staging, assessing the extent of infiltration into suggest malignant neoplasm, IDUS currently lacks the
extrahepatic and perihepatic lesions, and planning capability to acquire tissue samples. 92
various medical interventions. 80,81 Despite the diagnostic
advantages of ERC imaging, a study by Kalaitzakis 2.5. PET/CT
et al. showed that many patients with immunoglobulin PET is a non-invasive imaging method that provides
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G4-associated cholangitis can be misdiagnosed with functional images by detecting the uptake of the
biliary tract cancer. During ERC, biliary obstruction can radiolabeled 18F-fluorodeoxyglucose (FDG) in cancer
be relieved by placing a stent or drainage catheter, which cells. Over the past decade, integrated PET and CT (PET/
offers palliation for patients with an inoperable condition. 80 CT) imaging systems have enabled the acquisition of both
EUS is an alternative to ERC for diagnosing biliary tract anatomical and functional images. FDG-PET in oncology
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cancer. This technique allows for accurate evaluation is performed with the patient fasting and at rest, which
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of extrahepatic bile ducts, the gallbladder, hepatic hilar enhances the uptake of the tracer in tumor cells while
structures, regional lymph nodes, and adjacent vessels. minimizing its uptake by skeletal muscle. PET and PET/
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EUS plays a critical role in the diagnosis and staging of CT are now considered the standard methods for staging
biliary tract cancer, especially in assessing inoperable various malignancies and have also proven valuable
periampullary bile duct cancer for potential liver in the diagnosis and staging of biliary tract cancer. A
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transplantation. However, there is still a lack of data meta-analysis of the diagnostic accuracy of FDG-PET in
regarding the precise role of EUS in diagnosing biliary detecting primary biliary tract cancer demonstrated that
tract cancer in patients with unspecified extrahepatic the combined sensitivity and specificity of FDG-PET
biliary strictures. EUS has a tumor detection rate of were 95% and 83% for intrahepatic cancer, 84% and 95%
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Volume 3 Issue 1 (2025) 6 doi: 10.36922/arnm.4557