Pertuzumab was approved by the FDA in 2012 for use in combination with trastuzumab and docetaxel for patients with HER2-positive MBC who have not received prior anti-HER2 therapy or chemotherapy for metastatic disease, based on a multicenter, randomized, double-blind, placebo-controlled trial (CLEOPATRA) in which its addition to trastuzumab and docetaxel improved progression-free survival (HR = 0.62; 95% CI: 0.51–0.75; p < 0.0001) [74]. This evidence concerns the gene ERBB2 and metastatic neoplasm.