In a similar study by Choi and colleagues, breast cancer patients with pCR to neoadjuvant trastuzumab + pertuzumab treatment had a median HER2/CEP17 ratio of 7.08 and a median HER2 copy number of 17, whereas patients without pCR had a median ratio of 4.70 and a median copy number of 12 [21]. The gene discussed is ERBB2; the disease is breast cancer.