Abstract: Objective This study aims to explore the relationship between the degree of infiltration of CD8⁺ cytotoxic T lymphocytes in the tumor microenvironment of patients with primary liver cancer and their prognosis, with the hope of providing a new immunological basis for the treatment of liver cancer. Methods This study was retrospective, selecting 68 patients who underwent surgery for primary liver cancer between January 2018 and January 2020 as research subjects. Fresh liver tissues (including tumor and adjacent non-tumor tissues) were obtained during the surgery. Flow cytometry was used to assess the infiltration levels (IL) of CD8⁺ T cells in tumor tissues, adjacent non-tumor tissues. Patients were divided into recurrence (25 patients) and non-recurrence groups (43 patients) based on postoperative recurrence, and into survival (50 patients) and death groups (18 patients) based on final survival status. Clinical and pathological characteristics were statistically compared. All the above study subjects were followed up, with the follow-up period from January 2020 to January 2024. Cox regression analysis was utilized to examine factors affecting survival post-hepatectomy. Survival curves based on CD8⁺ T IL quantities were plotted using the Kaplan-Meier method, and differences were analyzed using the log-rank test. Results The recurrence group had 17 patients with ≤100 CD8⁺ T cells, fewer than the non-recurrence group′s 12 patients (P<0.05). The death group included 14 patients with tumors ≥5 cm, significantly more than the survival group (P<0.05), and 13 patients with ≥2 tumors, fewer than the 21 in the survival group (P<0.05). The death group also had 11 patients with encapsulated tumors, fewer than the survival group′s 13 patients (P<0.05), and 9 with tumor thrombi, the same number as the survival group but with statistical significance (P<0.05). Ten patients in the death group had postoperative alpha-fetoprotein (AFP) levels <400 ng/mL, fewer than the 31 in the survival group (P<0.05). Univariate and multivariate Cox regression analyses identified alpha-fetoprotein levels (P=0.041) and CD8⁺ T cell counts (P=0.009) as factors influencing recurrence post-surgery. Tumor size (P=0.001), capsule presence (P=0.037), serum AFP levels one month post-surgery (P=0.034), Edmondson-Steiner grading (P=0.013), and alpha-fetoprotein levels (P=0.013) were factors affecting mortality in univariate analysis, while AFP levels (P=0.009) and CD8⁺ T cell counts (P=0.006) were identified in multivariate analysis. Conclusion The level of CD8⁺ T cell infiltration in the tumor microenvironment of primary liver cancer patients is closely related to their prognosis. Higher levels of CD8⁺ T cell infiltration correlate with a better clinical outcome, suggesting that CD8⁺ T cells may be an important immunological target in liver cancer treatment.

Key words: Primary liver cancer, CD8⁺ cytotoxic T lymphocytes, Tumor microenvironment, Prognosis, Flow cytometry