Liu S, et al. – The role of tumor-infiltrating lymphocytes (TILs), particularly cytotoxic CD8+ T cells, was examined in the prediction of outcomes in patients with human epidermal growth factor receptor 2 (HER2)–positive metastatic breast cancer randomized to an antibody–based (trastuzumab) vs a small molecule–based (lapatinib) anti–HER2 therapy. As per findings, a low level of preexisting cytotoxic sTILs predicted the most benefit from an antibody– vs a small molecule–based drug against the same target