Prognostic impact of tumor-infiltrating lymphocytes in high grade serous ovarian cancer: a systematic review and meta-analysis

Background: Tumor-infiltrating lymphocytes (TILs) are involved in the antitumor immune response. The association between prognosis in patients with TILs and high-grade serous ovarian cancer (HGSOC) remains obscure, with some studies reporting conflicting results. Methods: We conducted an extensive literature search of electronic databases and retrieved prognostic data of each selected subtype of TILs, including CD3+, CD4+, CD8+, CD103+, and PD-1+ TILs. The fixed-effects model was applied to derive the pooled hazard ratio (HR) and 95% confidence interval (CI) of these markers. Results: The systematic review process yielded 19 eligible studies comprising 6004 patients with HGSOC. We compared TIL-positive and TIL-negative patients, and the pooled HRs from the multivariate analysis revealed that intraepithelial CD8+ TILs were positively correlated with progression-free survival (PFS, HR 0.46, 95% CI 0.25-0.67) and overall survival (OS, HR 0.90, 95% CI 0.86-0.9); stromal CD8+ TILs were positively correlated with OS (HR 0.61, 95% CI 0.36-0.87). Furthermore, the pooled HRs from univariate analysis demonstrated that intraepithelial CD3+, CD4+, CD8+, and CD103+ TILs were positively associated with OS (HR 0.58, 95% CI 0.44-0.72; HR 0.37, 95% CI 0.16-0.59; HR 0.51, 95% CI 0.42-0.60, and HR 0.59, 95% CI 0.44-0.74, respectively); stromal CD4+ and CD8+ TILs were significantly associated with OS (HR 0.63, 95% CI 0.32-0.94 and HR 0.78, 95% CI 0.58-0.97, respectively). However, the pooled HR from the multivariate analysis revealed that PD-1+ TILs were not associated with the OS of patients with HGSOC (HR 0.97, 95% CI 0.90-1.04). Conclusion: This meta-analysis provided evidence of the association of CD3+, CD4+, CD8+, and CD103+ TILs with the survival benefits (OS and PFS) of patients with HGSOC.