Utility of optimal proportion of tumor-infiltrating lymphocytes as a prognostic prediction of clinical outcome in intrahepatic cholangiocarcinoma: a single institution retrospective analysis

Intrahepatic cholangiocarcinoma (iCCA), prevalent in Northeastern Thailand, presents challenges due to late diagnosis and metastasis. Prognostic factors are crucial. Tumor-infiltrating lymphocytes (TILs) hold promise as prognostic indicators and for immunotherapy, but their optimal proportion in iCCA prognosis is yet to be determined. We propose to evaluate the optimal proportion of TILs for predicting the outcomes of iCCA. We analyzed TIL levels in 190 iCCA cases across four models with varying TIL cut-offs. Correlations with clinicopathological features were examined, followed by univariate and multivariate survival analyses. Subgroup analysis differentiated early and late-stage disease to assess TILs predictive potential. Results showed that at least 20% of TILs were significantly associated with smaller tumor size and growth patterns of intraductal (ID) and ID mixed types. Multivariate analysis revealed that 20%-40% of TILs were an independent factor for predicting good survival of patients. In addition, the 20% cut-off value was an independent factor for predicting the survival outcome of patients with early-stage disease. In this study, we identified the optimal proportion of stromal TILs for prognostic prediction in early-stage iCCA patients. Further research is warranted to validate the role of TILs as a prognostic biomarker and to explore their potential utility in guiding patient monitoring and risk stratification in early-stage disease.