Changes in Tumor-infiltrating Lymphocytes After Neoadjuvant Chemotherapy and Clinical Significance in Triple Negative Breast Cancer

Background/Aim: Neoadjuvant chemotherapy (NAC) can affect tumors and the tumor microenvironment. As changes in tumor-infiltrating lymphocytes (TILs) after NAC and the resulting clinical significance have not been clearly defined, we evaluated both in triple negative breast cancer (TNBC). Materials and Methods: TIL level was histologically analyzed in pre-NAC biopsy and post-NAC operation specimens from 104 TNBC cases with residual invasive carcinoma after NAC. Results: Forty-three cases (41.3%) showed decreases in TIL level, whereas 29 cases (27.9%) showed increases and no significant changes were found in 32 cases (30.8%). A decrease or increase in TIL levels corresponded to a better disease-free survival (DFS) as compared to unchanged levels. In multivariate analysis, a change in TIL level was an independent prognostic factor for DFS. Conclusion: We identified a prognostic significance of TIL changes after NAC. Assessment of TILs before and after NAC can provide valuable prognostic information for TNBC patients.