Prognostic impact of tumour-infiltrating immune cells on biliary tract cancer

Abstract

Background: Biliary tract cancers (BTC) are relatively rare malignant tumours with poor prognosis. It is known from other solid neoplasms that antitumour inflammatory response has an impact on tumour behaviour and patient outcome. The aim of this study was to provide a comprehensive characterisation of antitumour inflammatory response in human BTC.

Methods: Tumour-infiltrating T lymphocytes (CD4+, CD8+, and Foxp3+), natural killer cells (perforin+), B lymphocytes (CD20+), macrophages (CD68+) as well as mast cells (CD117+) were assessed by immunohistochemistry in 375 BTC including extrahepatic (ECC; n=157), intrahepatic (ICC; n=149), and gallbladder (GBAC; n=69) adenocarcinomas. Overall and intraepithelial quantity of tumour-infiltrating immune cells was analysed. Data were correlated with clinicopathological variables and patient survival.

Results: The most prevalent inflammatory cell type in BTC was the T lymphocyte. Components of the adaptive immune response decreased, whereas innate immune response components increased significantly in the biliary intraepithelial neoplasia - primary carcinoma - metastasis sequence. BTC patients with intraepithelial tumour-infiltrating CD4+, CD8+, and Foxp3+ T lymphocytes showed a significantly longer overall survival. Number of total intraepithelial tumour-infiltrating Foxp3+ regulatory T lymphocytes (HR: 0.492, P=0.002) and CD4+ T lymphocytes (HR: 0.595, P=0.008) were tumour grade- and UICC-stage-independent prognosticators. The subtype-specific evaluation revealed that the tumour-infiltrating lymphocytic infiltrate is a positive outcome predictor in ECC and GBAC but not in ICC.

Conclusion: Our findings characterise the immune response in cholangiocarcinogenesis and identify inflammatory cell types that influence the outcome of BTC patients. Further, we show that BTC subtypes show relevant differences with respect to density, quality of inflammation, and impact on patient survival.

Figure 1

Distribution of inflammatory cell infiltrates in non-invasive precursors (BilIN III), tumour margin, tumour centre, and metastatic lesions of BTC. Total number of CD4+ T lymphocytes (A), Foxp3+ regulatory T lymphocytes (B), CD8+ T lymphocytes (C), CD20+ B lymphocytes (D), CD68+ macrophages (E), CD117+ mast cells (F) in non-invasive precursors (BilIN III), tumour margin, tumour centre, and metastatic lesions of BTC.

Figure 2

Spearman's correlation between all assessed inflammatory parameters. Colours of cubes represent strength of correlation, with dark colours showing a high degree of association. In each cube, there are three values given: top=r, middle=p, and bottom=n.

Figure 3

Distribution of inflammatory cell infiltrates in biliary tract cancers (BTC) and subtypes. Total number of CD4+ T lymphocytes (A), CD8+ T lymphocytes (B), Foxp3+ regulatory T lymphocytes (C), CD20+ B lymphocytes (D), CD68+ macrophages (E), and CD117+ mast cells (F) in BTC, extrahepatic cholangiocarcinoma (ECC), adenocarcinoma of the gallbladder (GBAC), and intrahepatic cholangiocarcinoma (ICC).

Figure 4

Overall survival probability in BTC patients stratified for inflammatory cell infiltrates. Kaplan–Meier curves depict overall survival probability stratified for either intraepithelial (A, C, E, I, K) or total (B, D, F, G, H, J, L) immune cell infiltrate of CD4+ T lymphocytes (A, B), CD8+ T lymphocytes (C, D), Foxp3+ regulatory T lymphocytes (E, F). CD20+ B lymphocytes (G, H), CD68+ macrophages (I, J), and CD117+ mast cells (K, L). P-values were calculated with a log-rank test.