• Signed ICF; Women between 18-80 years of age at time of signing ICF.

• ECOG ≤ 1

• HER2+ breast cancer with clinical stage at presentation: T1cN1, T2, N0-1

• HER2 3+ by IHC, with strongly positive staining for HER2 protein in ≥ 80% of cells, and absence of HER2 negative areas in the tumor

• ER IHC ≤10%

• PR IHC negative (\<1%) or 0% of tumor cell nuclei

• Tumors must have at least 10mm measured by breast echography and be assessable for SUVMax (maximum standardized uptake value (SUVmax) ≥ 2.5) using 18FDG-PET-CT scan on baseline imaging.

• Availability of formalin-fixed, paraffin-embedded (FFPE) tumor tissue block for central confirmation of HER2 and hormone receptor status and additional biomarker research.

• Baseline LVEF ≥ 55% measured by echocardiogram (ECHO) or multiple-gated acquisition scan (MUGA).

• For women of childbearing potential (WOCBP) who are sexually active: agreement to remain abstinent (refrain from heterosexual intercourse) or use one highly effective non-hormonal contraceptive method with a failure rate of \< 1% per year, or two effective non-hormonal contraceptive methods during the treatment period and for 7 months after the last dose of HER2-targeted therapy, and agreement to refrain from donating eggs during this same period.

• A negative serum pregnancy test must be available prior to randomization for WOCBP (premenopausal women and women \< 12 months after the onset of menopause), unless they have undergone surgical sterilization (removal of ovaries and/or uterus)