Prognostic value of tumor-infiltrating lymphocytes in DCIS: a meta-analysis

Background Tumor infiltrating lymphocytes (TILs) have been shown 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 precise than the TIL ratio (HR 1.49 (95% CI 1.11-1.99)) in estimating DCIS recurrence risk. Moreover, the prognostic value of TILs seemed more 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)), than 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 suggested a non-favorable prognosis of TILs and stromal PD-L1+ TILs in DCIS and indicated an appropriate assessment method for TILs and an eligible population.