Prognostic relevance of increased tumor-infiltrating lymphocytes in residual TNBC following neoadjuvant chemotherapy

This study evaluated the predictive value of tumor-infiltrating lymphocytes (TILs) in residual triple-negative breast cancer (TNBC) following neoadjuvant chemotherapy (NAC). Patients with TNBC treated between 2008 and 2019 who presented with residual disease after NAC were included. Tumor samples were assessed before and after treatment, with TILs quantified as the percentage of mononuclear inflammatory cells in the tumor stroma. TILs levels were analyzed as both continuous and categorical variables (high ≥ 30%, low < 30%). Among the 60 patients evaluated, the mean age was 52.6 ± 1.2 years (range: 28–78 years), with most receiving standard NAC, consisting of anthracycline and cyclophosphamide followed by docetaxel. A significant increase in TILs levels post-NAC was observed, with 55% of tumors classified as high TILs, compared to 90% classified as low TILs before treatment (McNemar’s test, p ≤ 0.0001). However, post-NAC TILs increase was not statistically associated with disease-free survival or overall survival. These findings suggest an immunologic modulation of the tumor microenvironment in residual TNBC, highlighting the potential role of identifying immune-enriched residual tumors as candidates for adjuvant strategies, including immunotherapy.