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

Participants will be randomized in 1:1 ratio to receive pertuzumab or placebo along with
trastuzumab and docetaxel every 3 weeks (Q3W) in the treatment phase of the study until
investigator-assessed radiographic or clinical progressive disease, unmanageable toxicity, or
study termination. Participants who were on placebo arm will be offered to receive after
completion of treatment phase but participants who discontinue from the study, will not
receive pertuzumab during open-label phase.

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)

- HER2-positive 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, agreement to use an effective form of
contraception and to continue its use for the duration of study treatment and for 6
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)

- 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 or basal cell carcinoma

- 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

- 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 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