Treating the HER2 pathway in early and advanced breast cancer.

ERBB2 gene amplification occurs in ∼20% of human breast cancers (BC) and is associated with an adverse clinical prognosis, indicating that it may be playing a critical role in disease pathogenesis. Therapeutic strategies targeting pathologic ERBB2 overexpression have revolutionized the diagnosis and treatment of BC. Indeed, humanized anti-ERBB2 antibodies, small molecule ERBB2 kinase inhibitors and ERBB2-targeting antibody-drug conjugates have proven safety and efficacy based upon evidence from randomized phase III clinical trials. Recent progress in targeting ERBB2 alteration will be reviewed, with focus on data that has informed changes in clinical practice for the treatment of BC.