High FOXP3+ and Low KI-67 Expression as Risk Factors for Poor Response to Neoadjuvant Chemotherapy in Triple-Negative Breast Cancer (TNBC)

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options and poor prognosis. Neoadjuvant chemotherapy (NAC) is standard for TNBC, though response rates vary widely. This study investigates high FOXP3+ and low Ki-67 expressions as potential predictors of poor NAC response in TNBC. Methods: This case-control study included 70 TNBC patients who received NAC. Based on NAC response, patients were categorized as cases (poor response) or controls (good response) per RECIST 1.1 criteria. FOXP3 and Ki-67 levels were assessed via immunohistochemistry, with FOXP3 classified as high (>2) or low (≤2) and Ki-67 as high (>20%) or low (≤20%). Associations between marker levels and NAC response were analyzed using chi-square and Fisher’s exact tests, with significance at p < 0.05. Results: High FOXP3+ expression was significantly associated with poor NAC response (OR=4.231, p=0.004), indicating a fourfold increased risk. However, low Ki-67 expression was not a significant predictor of NAC response (p=0.710). These findings highlight FOXP3+ as a relevant factor in NAC outcomes, while Ki-67 lacks independent predictive value in TNBC. Conclusion: High FOXP3+ expression is a significant predictor of poor NAC response in TNBC, likely due to its immunosuppressive effects. FOXP3+ could serve as a biomarker for refining NAC strategies in TNBC, while Ki-67 appears less predictive.