When to Add Additional Anti-HER2 Therapy to Adjuvant Trastuzumab

Purpose of Review: One year of trastuzumab dramatically improves outcomes in early HER2 positive breast cancer, irrespective of anatomic stage, receptor status and chemotherapy backbone. However, up to 25% of breast cancers treated with trastuzumab and chemotherapy recur. Here, we review the current role for additional HER2 blockade to adjuvant trastuzumab. Recent Findings: Adjuvant pertuzumab and neratinib modestly improve disease-free survival in early breast cancer, particularly for those at highest risk of recurrence. Lack of complete pathologic response to preoperative chemotherapy and HER2 targeted therapies is associated with worse outcomes. In those with lack of pCR, adjuvant trastuzumab emtansine improves outcome in early breast cancer, irrespective of chemotherapy and HER2 targeted therapy backbone. Summary: Preoperative chemotherapy and HER2 targeted therapy should be discussed in early breast cancer, especially in tumors over 2 cm. Future trials must focus on de-escalation of chemotherapy and biomarkers for further tailored therapy in early HER2 positive breast cancer.