A Study To Evaluate the Efficacy and Safety Of Atezolizumab or Placebo in Combination With Neoadjuvant Doxorubicin + Cyclophosphamide Followed By Paclitaxel + Trastuzumab + Pertuzumab In Early Her2-Positive Breast Cancer

Inclusion Criteria:

- Confirmed diagnosis of HER2-positive breast cancer, and hormonal and PD-L1 status, as
documented through central testing of a representative tumor tissue specimen

- Primary breast tumor size of > 2 cm by radiographic measurement

- Stage at presentation: T2-T4, N1-N3, M0 as determined by AJCC staging system, 8th
edition

- Pathologic confirmation of nodal involvement with malignancy must be determined by
fineneedle aspiration or core-needle biopsy. Surgical excision of lymph nodes is not
permitted.

- Patients with multifocal tumors or multicentric tumors are eligible provided all
discrete lesions are sampled and centrally confirmed as HER2-positive.

- Patients with synchronous bilateral invasive disease are eligible so long as both
lesions are HER2-positive.

- Eastern Cooperative Oncology Group Performance Status of 0 or 1

- Baseline LVEF >= 55% measured by echocardiogram (ECHO) or multiple-gated acquisition
(MUGA) scans

- Adequate hematologic and end-organ function obtained within 14 days prior to
initiation of study treatment

- For women of childbearing potential: agreement to remain abstinent or use
contraceptive methods, and agreement to refrain from donating eggs

- For men: agreement to remain abstinent or use contraceptive measures, and agreement to
refrain from donating sperm

Exclusion Criteria:

- Prior history of invasive breast cancer

- Stage IV (metastatic) breast cancer

- Prior systemic therapy for treatment of breast cancer

- Previous therapy with anthracyclines or taxanes for any malignancy

- Ulcerating breast cancer

- Undergone incisional and/or excisional biopsy of primary tumor and/or axillary lymph
nodes

- Sentinel lymph node procedure or axillary lymph node dissection prior to initiation of
neoadjuvant therapy

- History of other malignancy within 5 years prior to screening, with the exception of
those patients who have a negligible risk of metastasis or death

- Cardiopulmonary dysfunction

- Dyspnea at rest

- Active or history of autoimmune disease or immune deficiency

- Pregnancy or breastfeeding, or intention of becoming pregnant during study treatment
or within 5 months after the final dose of atezolizumab/placebo, 6 months after the
final dose of doxorubicin, 12 months after the final dose of cyclophosphamide, 6
months after the final dose of paclitaxel, or 7 months after the final dose of
trastuzumab and/or pertuzumab, whichever occurs last