Background: Tumour-infiltrating lymphocytes CD8+ (TILs CD8+) as an anticancer immune response and Programmed Death-Ligand 1 (PD-L1) as an immune checkpoint molecule expression are important in colorectal cancer (CRC) as their expression correlates with the immune status and the progression of cancer. The primary objective of this study is to examine the relationship between TILs CD8+ and PD-L1 expression levels and CRC metastasis to provide insights into the immune microenvironment’s role in CRC progression and metastasis, potentially improving patient outcomes and treatment response. Methods: This study was an observational study involving colorectal cancer patients who were treated at a tertiary hospital in Bandung, West Java, Indonesia. There were 40 patients included in the study. Tumour tissue samples were collected from patients, and immunohistochemical staining was performed to evaluate TILs CD8+ infiltration and PD-L1 expression levels. Clinical data, including metastasis occurrences, were collected from the cancer registry. Results: Analysis of TILs CD8+ and PD-L1 expression levels in CRC patients revealed significant findings regarding metastasis occurrence and cancer staging. There was a notable positive correlation between PD-L1 expression and TILs-CD8+ infiltration in the presence of distant metastasis and advanced cancer stage (p < 0.05). However, no significant association was observed between TILs CD8 and PD-L1 expression levels and lymphatic metastasis. Conclusion: This study highlights the potential prognostic value of TILs CD8+ and PD-L1 expression levels in predicting CRC progression and metastasis. However, the lack of a significant correlation with lymphatic metastasis suggests the need for further investigation into the underlying mechanisms. Understanding the roles of PD-L1 and TILs-CD8+ expression in CRC metastasis may facilitate the development of targeted therapeutic strategies to improve patient outcomes.

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