Tumor-infiltrating lymphocytes as predictive biomarkers in neoadjuvant treatment of HER2-positive breast cancer

BACKGROUND: Tumor-infiltrating lymphocytes (TILs) have emerged as predictive biomarkers in HER2-positive breast cancer, correlating with treatment response and survival outcomes. This study evaluates the impact of TIL levels and Ki67 suppression on neoadjuvant therapy efficacy in this patient population. MATERIALS AND METHODS: A retrospective analysis of 136 HER2-positive breast cancer patients was conducted. Patients were stratified by TIL levels, and clinical outcomes, including Ki67 expression, pathological complete response (pCR), and disease-free survival (DFS), were assessed. RESULTS: High TIL levels (≥ 40%) were significantly associated with higher pCR rates (60.32% vs. 39.73%, P = .02) and with TIL ≥ 10% greater Ki67 suppression. In patients with low TIL levels, high Ki67 expression correlated with better pCR rates (57.1% vs 30.8%, P = 0.010), while in high TIL patients, no significant difference was observed between high and low Ki67 groups (P = 0.317). A trend toward improved DFS was noted in the high TIL group, with 3-year survival rates of 91.9% vs. 80.7% in the low TIL group, though this was not statistically significant (P = .062). CONCLUSION: TIL levels are robust predictors of pCR and Ki67 suppression in HER2-positive breast cancer, particularly in patients with high initial TILs. These findings highlight the potential for integrating TIL evaluation into personalized treatment strategies to optimize neoadjuvant therapy outcomes. Further research is warranted to validate these results and explore underlying mechanisms.