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