De-escalation Neoadjuvant Therapy for Intermediate Risk HER2-positive Early Breast

High pathological complete response (pCR) rates are seen using different neoadjuvant chemotherapy schedules with trastuzumab and pertuzumab in HER2-positive stage II-III breast cancer patients. Total pCR rates in breast and axilla have been described as high as 64%, and with an even higher rate of \>80% in patients with HER2-positive and hormone receptor (HR) negative tumors. pCR is associated with better long-term outcomes in patients with HER2-positive breast cancer. Neoadjuvant treatment of HER2-positive breast cancer typically consists of six cycles of treatment. Longer duration of treatment is associated with higher pCR-rates but also with increased toxicity. It is therefore important to investigate which patients can safely be treated with less than six cycles of chemotherapy and which patients require six cycles for maximum efficacy.It is hypothesized that patients with a complete pathologic response may not benefit from additional chemotherapy, while those with residual invasive disease require further treatment. This study will evaluate de-escalation of the number of neoadjuvant chemotherapy cycles in intermediate risk HER2-positive breast cancer.