High tumor mutation burden indicates a poor prognosis in patients with intrahepatic cholangiocarcinoma

Background: Intrahepatic cholangiocarcinoma (ICC) is malignancies of the biliary duct system and constitutes approximately 10%-20% of all primary liver cancers. Tumor mutation burden (TMB) is a useful biomarker across many cancer types for the identification of patients who will benefit from immunotherapy. Despite the role of TMB in calculating the effectiveness and prognosis of immune checkpoint inhibitors has been confirmed in multiple human cancer types, the prognostic value of TMB in ICC patients is rare investigated.

Aim: To investigate the prognostic value of TMB in patients with ICC.

Methods: Data of 412 patients with ICC were included in the study. TMB was calculated as the total number of somatic non-silent protein-coding mutations divided by the coding region. The Kaplan-Meier method was used to analyze overall survival (OS), and relapse free survival (RFS). The cut-off value of TMB was determined by time-dependent receiver operating characteristic (ROC) curve. Cox regression was performed for multivariable analysis of OS. The nomogram and calibration curve were analyzed to construct and evaluate the prognostic model.

Results: In the analysis of the time-dependent ROC curve, we defined 3.1 mut/Mb as the cut-off value of TMB. The Kaplan-Meier plot revealed that patients with high TMB had poor OS (HR = 1.47, P = 0.002) and RFS (HR = 1.42, P = 0.035). Cox regression analysis also demonstrated that TMB was an independent risk predictor for ICC (HR = 1.43, P = 0.0240). Furthermore, independent prognostic factors of ICC included CA19-9 (HR = 1.78, P = 0.0005), chronic viral hepatitis (HR = 1.72, P = 0.0468), tumor resection (HR = 2.58, P < 0.0001) and disease progression (metastatic disease vs. solitary liver tumor; HR = 2.55, P = 0.0002). The nomogram and calibration curve also indicated the effectiveness of the constructed prognostic model.

Conclusion: TMB was an independent prognostic biomarker in patients with ICC. Moreover, patients with ICC with high TMB had poor OS and RFS as compared to those with low TMB.