Systemic Therapy Advances for HER2-Positive and Triple Negative Breast Cancer: What the Surgeon Needs to Know.

Neoadjuvant systemic therapy (NST) was initially reserved for unresectable patients however it has been increasingly used to facilitate breast conservation, downstage the axilla, and inform adjuvant therapy decisions based on response. For patients with HER2+ and triple-negative breast cancer (TNBC), clinical trials have resulted in the ability to individualize treatment regimens. For HER2+ breast cancer, de-escalation of neoadjuvant regimens to minimize cytotoxic chemotherapy and de-escalation or escalation of adjuvant regimens based on response have been effective. For TNBC, the approval of the combination of chemotherapy plus immunotherapy in the neoadjuvant setting has resulted in a major practice shift and opened the door to many additional treatment questions including de-escalation of the chemotherapy backbone or the adjuvant regimen. For both HER2+ and TNBC, most patients are treated with NST except those with very small tumors. Efforts are also being made to optimally identify patients with T1c tumors who may benefit from more aggressive NST. For patients treated according to or enrolled in NST de-escalation trials, breast conservation (even those who become eligible based on response to NST) and sentinel lymph node biopsy when cN0 at the completion of NST are safe and feasible. Continued involvement of surgeons and multidisciplinary teams in the design and reporting of trials will streamline their adoption into clinical practice. Surgeons need to remain aware of ongoing systemic therapy trials to appropriately select patients for NST and plan for appropriate post-neoadjuvant surgical care.