Tumor-Infiltrating Lymphocytes and Associations With Pathological Complete Response and Event-Free Survival in HER2-Positive Early-Stage Breast Cancer Treated With Lapatinib and Trastuzumab

Abstract

The presence of tumor-infiltrating lymphocytes (TILs) has been shown to have significant positive prognostic relevance for certain subtypes of breast cancer.^1-5 Tumor-infiltrating lymphocytes have also been reported to be associated with improved distant metastases–free survival in patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer, as well as increased rates of pathological complete response (pCR) with neoadjuvant trastuzumab and chemotherapy.^1-3 Increasingly, oncogenic addiction, in which tumors become dependent on a sole oncogenic pathway for growth, is thought to also promote a tumor microenvironment conducive to immune escape.^6,7 Although this has not been shown yet for HER2 oncogenic signaling, one could speculate that anti-HER2 therapy may not only work in a cell-intrinsic manner but may also reverse HER2-induced immunosuppression as a mechanism of action.