ERBB2 and breast cancer: Furthermore, a combined examination of individual patient data from four prospective neoadjuvant clinical trials, encompassing a cohort of 2,310 patients diagnosed with HER2-non-amplified primary breast cancer and treated with neoadjuvant chemotherapy, revealed that tumors characterized by HER2-low-positive expression exhibited a notably reduced rate of pathological complete response compared to HER2-negative tumors (12).