Stromal Tumor-Infiltrating Lymphocytes Level As a Prognostic Factor for Resected Intrahepatic Cholangiocarcinoma and Its Prediction by Apparent Diffusion Coefficient

Background Tumor-infiltrating lymphocytes (TILs) are a prognostic factor or an indicator of chemotherapy response for various malignancies. The aim of this study was to investigate the prognostic impact of TILs in resected intrahepatic cholangiocarcinoma (IHCC). We also investigated the usefulness of the apparent diffusion coefficient (ADC) in diffusion-weighted magnetic resonance imaging (DW-MRI) to predict TILs. Methods We enrolled 23 patients with IHCC who underwent initial hepatic resection in Tokushima University Hospital from 2006 to 2017. We evaluated stromal TILs in the tumor marginal area and central area in surgical specimens. Patients were divided into low vs high stromal TILs groups. We analyzed the patients’ clinicopathological factors, including prognosis, according to the degree of stromal TILs. We also analyzed the correlation between stromal TILs and the minimum ADC value. Results Stromal TILs in the marginal area reflected overall survival more accurately than that in the central area. Additionally, marginal low TILs was significantly associated with lymph node metastasis and portal vein invasion. Both overall- and disease-free survival rates in the marginal low TILs group were significantly worse than those in the marginal high TILs group ( P < 0.05). In the multivariate analysis, marginal low TILs were an independent prognostic factor for both overall- and disease-free survival ( P < 0.05), and marginal low TILs were significantly associated with lower minimum ADC values ( P < 0.02). Conclusions Stromal TILs, especially in the marginal area, might demonstrate prognostic impact in patients with IHCC. Moreover, the ADC values from MRI may predict TILs in IHCC tumor tissue.