In the clinical assessment of CLEOPATRA (clinical evaluation of docetaxel, pertuzumab, and trastuzumab), a double-blind randomized phase III trial comparing pertuzumab and trastuzumab+docetaxel with placebo+trastuzumab+docetaxel as the primary treatment for HER2-positive progressive and recurrent breast cancer, the response rates (RR) were 80.2% and 69.3% in the pertuzumab and control groups, respectively. Here, ERBB2 is linked to breast cancer.