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