The Prognostic and Predicting Roles of Tumor-Infiltrating Lymphocytes in Breast Cancer: A Meta-Analysis

Background: The relationship between lymphocyte infiltrates (LIs) and breast cancer outcome remains controversial. We performed this meta-analysis to elucidate the relationship. Methods: A literature search identified 21 eligible studies. Results: 16,097 patients were included. Multivariate analyses data for patients with unspecified receptors status showed that rich LIs expression was associated with 52% (hazard ratio (HR) = 0.48; 95% confidence interval (CI), 0.30-0.77), and 29% (HR = 0.71; 95% CI, 0.63-0.80) reduction in the risk of relapse and death, respectively. In the neoadjuvant setting, rich LIs predicted a 28% increase in complete pathological response rate. The prognostic and predictive utility of rich LIs was restricted to patients with estrogen receptor negative (ER-) or triple negative disease. Only rich CD8+ T cells tumors demonstrated clinical utility. Conclusion: LIs significantly correlated to outcome predominantly in ER- tumors. Integrating immunotherapy with conventional therapy may warrant future research in breast cancer.