ERBB2 and breast cancer: Elsewhere in the literature, in a prospective study carried out in non-metastatic BC patients after cystectomy, a research team analyzed the human epidermal growth factor receptor 2 (HER-2) expression in CTCs, showing that the HER2-positive CTC group could benefit from targeted therapies; however, HER-2-negative CTCs conferred resistance against immunotherapy to patients with HER-2-positive primary tumors.