Prognostic Role of Tumor-Infiltrating Lymphocytes in Lung Cancer: a Meta-Analysis

Background/aims: The role of Tumor-infiltrating lymphocytes (TILs) in the prognosis of patients with lung cancer is still controversial. We performed a meta-analysis to evaluate the prognostic role of TILs in lung cancer.

Methods: Studies were recruited by searching PubMed, Embase and the Cochrane Library and assessed by further quality evaluation. The pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated to investigate the association between TIL subsets and lung cancer patients' outcome.

Results: A total of 29 articles including 8,600 patients were enrolled into the meta-analysis. Our results indicated that high level of CD8+ cells infiltration in tumor stroma (TS) or tumor nest (TN) was associated with better OS in lung cancer patients (HR = 0.76, 95% CI 0.62-0.93, P = 0.006; HR = 0.80, 95% CI 0.67-0.96; P = 0.018, respectively). Similar results could be also observed in CD3+ T cells infiltration. High CD4+ T lymphocytes infiltration in TS was explicitly accompanied by better OS (HR = 0.65, 95% CI 0.46-0.91; P = 0.013), rather than in TN. In contrast, high density of FOXP3+ T cells infiltration in TS showed a poor PFS (HR = 2.67, 95% CI, 1.74-4.08, P < 0.001).

Conclusion: This meta-analysis clarified that high level of CD8+ and CD3+ T cells infiltration in TS or TN, and high CD4+ T lymphocytes infiltration in TS showed better OS in lung cancer patients, whereas high density of FOXP3+ T cells infiltration in TS could be recognized as a negative prognostic factor.