A Study to Evaluate Pertuzumab + Trastuzumab + Docetaxel vs. Placebo + Trastuzumab + Docetaxel in Previously Untreated HER2-Positive Metastatic Breast Cancer

Inclusion Criteria

• Histologically or cytologically confirmed adenocarcinoma of the breast with locally recurrent or metastatic disease, and candidate for chemotherapy. Participants with measurable and non-measurable disease are eligible (locally recurrent disease must not be amenable to resection with curative intent; participants with de novo Stage IV disease are eligible)
• Human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC)
• Left ventricular ejection fraction (LVEF) ≥50 percent (%) at baseline (within 42 days of randomization)
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1
• For women of childbearing potential and men with partners of childbearing potential, agreement to use a highly effective form of contraception and to continue its use for the duration of study treatment and for at least 7 months after the last dose of study treatment

Exclusion Criteria

• History of anti-cancer therapy for MBC (with the exception of one prior hormonal regimen for MBC, which must be stopped prior to randomization)
• History of approved or investigative tyrosine kinase/HER inhibitors for breast cancer in any treatment setting, except trastuzumab used in the neoadjuvant or adjuvant setting
• History of systemic breast cancer treatment in the neo-adjuvant or adjuvant setting with a disease-free interval from completion of the systemic treatment (excluding hormonal therapy) to metastatic diagnosis of less than (<)12 months
• History of persistent Grade ≥2 hematologic toxicity resulting from previous adjuvant therapy
• Current peripheral neuropathy of National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE) Version 3.0, Grade ≥3 at randomization
• History of other malignancy within the last 5 years, except for carcinoma in situ of the cervix, basal cell carcinoma or squamous cell carcinoma of the skin that has been previously treated with curative intent
• Current clinical or radiographic evidence of central nervous system (CNS) metastases
• Computed tomography (CT) or magnetic resonance imaging (MRI) scan of the brain is mandatory in cases of clinical suspicion of brain metastases
• History of exposure to cumulative doses of anthracyclines
• Current uncontrolled hypertension or unstable angina
• History of congestive heart failure (CHF) of any New York Heart Association (NYHA) criteria, or serious cardiac arrhythmia requiring treatment (exception: atrial fibrillation or paroxysmal supraventricular tachycardia)
• History of myocardial infarction within 6 months of randomization
• History of LVEF decline to below 50% during or after prior trastuzumab neo-adjuvant or adjuvant therapy
• Current dyspnea at rest due to complications of advanced malignancy, or other diseases that require continuous oxygen therapy
• Inadequate organ function, as defined in the protocol, within 28 days prior to randomization
• Current severe, uncontrolled systemic disease
• Major surgical procedure or significant traumatic injury within 28 days prior to study treatment start or anticipation of the need for major surgery during the course of study treatment
• Pregnant or lactating women
• History of receiving any investigational treatment within 28 days of randomization
• Current known infection with human immunodeficiency virus (HIV), hepatitis B virus (HBV), or hepatitis C virus (HCV)
• Receipt of IV antibiotics for infection within 14 days of randomization
• Current chronic daily treatment with corticosteroids (excluding inhaled steroids)
• Known hypersensitivity to any of the study drugs
• Assessed by the investigator to be unable or unwilling to comply with the requirements of the protocol