Prognostic Value of Tumor-Infiltrating Lymphocytes in DCIS: A Meta-Analysis

Background: Tumor infiltrating lymphocytes (TILs) have been demonstrated to be associated with the prognosis of breast ductal carcinoma in situ (DCIS). In this systematic review and meta-analysis, we investigated the role of TILs and TIL subsets in predicting the recurrence risk of DCIS. Method: PubMed, Medline, Web of Science, Embase and Cochrane were searched to identify publications investigating the prognostic role of TILs in DCIS. After study screening, data extraction and risk of bias assessment, a meta-analysis was performed to assess the association between TILs (total TILs, CD4+, CD8+, FOXP3+, PD-L1+ TILs) and the risk of DCIS recurrence. Results: A pooled analysis indicated that dense stromal TILs in DCIS were associated with a higher recurrence risk (HR 2.11 (95% CI 1.35-3.28)). Subgroup analysis showed that touching TILs (HR 4.73 (95% CI 2.28-9.80)) was more favorable than the TIL ratio (HR 1.49 (95% CI 1.11-1.99)) in estimating DCIS recurrence risk. Moreover, the predictive value of TILs is suitable for patients who are diagnosed with DCIS and then undergo surgery (HR 2.77, (95% CI 1.26-6.07)) or surgery accompanied by radiotherapy (HR 2.26, (95% CI 1.29-3.95)), but not for patients who receive comprehensive adjuvant therapies (HR 1.16, (95% CI 1.35-3.28)). Among subsets of TILs, dense stromal PD-L1+ TILs were valuable in predicting higher recurrence risk of DCIS. Conclusion: This systematic review and meta-analysis confirmed the predictive value of TILs and stromal PD-L1+ TILs in DCIS and indicated an appropriate assessment method for TILs and an eligible population.