Tumor-Infiltrating Lymphocytes in Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Receiving Neoadjuvant Docetaxel, Carboplatin, Trastuzumab, and Pertuzumab

PURPOSE: The tumor-infiltrating lymphocytes (TILs) expression in breast cancer is a positive prognostic marker for certain breast cancer subtypes. We evaluated the efficacy of dual anti-human epidermal growth factor receptor 2 (HER2) blockade in HER2-positive breast cancer and hypothesized that high TILs tumors are associated with better outcomes. METHODS: A total of 176 patients who were treated with neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab (TCHP) between December 2015 and December 2018 were reviewed. They were grouped based on a cut-off value of the stromal TILs grade (≤ 20% TILs, > 20% TILs). RESULTS: In total, 107 patients (60.8%) achieved pathological complete response (pCR). Hormone receptor (HR)-negativity (p = 0.001) and a high TILs grade (p = 0.022) were independent predictors of pCR. Among the HR-negative patients, high TILs tumors were significantly associated with pCR (p = 0.035). CONCLUSION: HR status and the TILs grade are significantly correlated with pCR in dual anti-HER2 neoadjuvant therapy. The evaluation of the TILs at baseline may be beneficial for predicting pCR in HER2-positive breast cancer.