Evaluation of the diagnostic performance of apparent diffusion coefficient (ADC) values on diffusion-weighted magnetic resonance imaging (DWI) in differentiating between benign and metastatic lymph nodes in cases of cholangiocarcinoma.

Abstract

Cholangiocarcinoma (CCA) is the primary tumor found in the bile duct and is associated with a high incidence of lymph node (LN) metastases and poor outcomes. The presence of metastatic lymph nodes, when shown by imaging, can influence patient treatment and prognosis. DWI is a promising, non-invasive imaging technique for differentiating between benign and malignant LNs. Many studies have shown that LN metastases have a lower apparent diffusion coefficient (ADC) value when compared to benign nodes. To evaluate the performance of ADC values as a basis for diagnosis of LN metastasis in cholangiocarcinoma patients. This was a retrospective imaging study that evaluated histopathologically proven intraabdominal LNs in cholangiocarcinoma patients who underwent a 1.5T abdomen MRI with DWI between January 2012 and July 2016. The ADC values and short-axis diameters of the LNs were measured and compared using student's t test. Receiver operating characteristic (ROC) curves were used to determine the threshold. A total of 120 lymph nodes-85 benign and 35 metastatic-were included. The mean short-axis diameter of the benign LNs (8.34mm) was significantly lesser than that of the malignant LNs (9.56mm). Receiver operating characteristic curve analysis using a size criterion of 1cm yielded a value of 0.63. A diagnostic size criterion of 1cm for the short axis was applied and yielded an accuracy of 66%, sensitivity/specificity of 41%/75%, and positive/negative predictive value of 34%/80%. The mean ADC values of metastatic (1.31 × 10-3mm2/s) LNs were not significantly different from those of non-metastatic LNs (1.29 × 10-3mm2/s). There was no difference in terms of ADC value between benign lymph nodes and those with metastatic cholangiocarcinoma. Isolated measurement of the ADC value does not contribute to a diagnosis of lymph node metastasis.