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 locallyrecurrent or metastatic disease, and candidate for chemotherapy. Participants withmeasurable and non-measurable disease are eligible (locally recurrent disease must notbe amenable to resection with curative intent; participants with de novo Stage IVdisease 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 daysof 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 forthe duration of study treatment and for at least 7 months after the last dose of studytreatment

Exclusion Criteria:

• History of anti-cancer therapy for MBC (with the exception of one prior hormonalregimen for MBC, which must be stopped prior to randomization)

• History of approved or investigative tyrosine kinase/HER inhibitors for breast cancerin any treatment setting, except trastuzumab used in the neoadjuvant or adjuvantsetting

• History of systemic breast cancer treatment in the neo-adjuvant or adjuvant settingwith a disease-free interval from completion of the systemic treatment (excludinghormonal therapy) to metastatic diagnosis of less than (<)12 months

• History of persistent Grade ≥2 hematologic toxicity resulting from previous adjuvanttherapy

• Current peripheral neuropathy of National Cancer Institute-Common Terminology Criteriafor 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 ofthe cervix, basal cell carcinoma or squamous cell carcinoma of the skin that has beenpreviously 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 ismandatory 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: atrialfibrillation 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 oradjuvant therapy

• Current dyspnea at rest due to complications of advanced malignancy, or other diseasesthat require continuous oxygen therapy

• Inadequate organ function, as defined in the protocol, within 28 days prior torandomization

• Current severe, uncontrolled systemic disease

• Major surgical procedure or significant traumatic injury within 28 days prior to studytreatment start or anticipation of the need for major surgery during the course ofstudy 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 requirementsof the protocol