A Study to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Administration of the Fixed-Dose Combination of Pertuzumab and Trastuzumab in Combination With Chemotherapy in Participants With HER2-Positive Early Breast Cancer

Inclusion Criteria

• Ability to comply with the study protocol, in the investigator's judgment
• Eastern Cooperative Oncology Group (ECOG) Performance Status ≤1
• Female and male patients with Stage II - IIIC (T2-T4 plus any N, or any T plus N1-N3, M0), locally advanced, inflammatory, or early-stage, unilateral, and histologically confirmed invasive breast cancer
• Primary tumor >2 cm in diameter, or node-positive disease (clinically or on imaging, and node positivity confirmed with cytology and/or histopathology)
• HER2-positive breast cancer confirmed by a central laboratory prior to study enrollment. HER2-positive status will be determined based on pretreatment breast biopsy material.
• Hormone receptor status of the primary tumor, centrally confirmed
• Patient agreement to undergo mastectomy or breast conserving surgery after neoadjuvant therapy
• Availability of formalin-fixed, paraffin-embedded (FFPE) tumor tissue block for central confirmation of HER2 and hormone receptor status and additional biomarker research
• Baseline left ventricular ejection fraction (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 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
• For men: men must remain abstinent or use a condom with a spermicidal product during the treatment period and for 7 months after the last dose of HER2-targeted therapy to avoid exposing the embryo. Men must refrain from donating sperm during this same period.
• A negative serum pregnancy test must be available prior to randomization for WOCBP, unless they have undergone surgical sterilization
• No major surgical procedure unrelated to breast cancer within 28 days prior to randomization or anticipation of the need for major surgery during the course of study treatment

Exclusion Criteria

• Stage IV (metastatic) breast cancer
• Patients with a history of invasive breast cancer
• Patients with a history of concurrent or previously treated non-breast malignancies except for appropriately treated 1) non-melanoma skin cancer and/or 2) in situ carcinomas, including cervix, colon, and skin
• Patients who have received any previous systemic therapy for treatment or prevention of breast cancer, or radiation therapy for treatment of cancer
• Patients who have a past history of ductal carcinoma in situ or lobular carcinoma in situ if they have received any systemic therapy for its treatment or radiation therapy to the ipsilateral breast
• Patients with high-risk for breast cancer who have received chemo-preventative drugs in the past are not allowed to enter the study
• Patients with multicentric breast cancer, unless all tumors are HER2-positive
• Patients with bilateral breast cancer
• Patients who have undergone an excisional biopsy of primary tumor and/or axillary lymph nodes
• Axillary lymph node dissection prior to initiation of neoadjuvant therapy
• Sentinel lymph node biopsy prior to neoadjuvant therapy
• Treatment with any investigational drug within 28 days prior to randomization
• Serious cardiac illness or medical conditions
• Inadequate bone marrow function, renal function or impaired liver function
• Current severe, uncontrolled systemic disease that may interfere with planned treatment
• Pregnant or breastfeeding, or intending to become pregnant during the study or within 7 months after the last dose of HER2-targeted therapy
• Any serious medical condition or abnormality in clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study
• Known active liver disease, for example, active viral hepa