A Study Comparing Atezolizumab (Anti PD-L1 Antibody) In Combination With Adjuvant Anthracycline/Taxane-Based Chemotherapy Versus Chemotherapy Alone In Patients With Operable Triple-Negative Breast Cancer

Inclusion Criteria:

• Non-metastatic operable Stage II-III breast cancer

• Histologically documented TNBC (Triple Negative Breast Cancer)

• Confirmed tumor PD-L1 evaluation as documented through central testing of a representative tumor tissue specimen

• Adequately excised: Patients must have undergone either breast-conserving surgery or mastectomy/nipple- or skin-sparing mastectomy

• Adequate hematologic and end-organ function

• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures

• For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures and agreement to refrain from donating sperm.

• No more than 8 weeks (56 days) may elapse between definitive breast surgery and randomization.

• Representative formalin-fixed, paraffin embedded (FFPE) tumor specimen from surgical resection in paraffin blocks (preferred) or at least 25 unstained slides.

Exclusion Criteria

• Prior history of invasive breast cancer

• For the currently diagnosed breast cancer, any previous systemic anti-cancer treatment (e.g., neoadjuvant or adjuvant), including, but not limited to, chemotherapy, anti-HER2 therapy.

• Previous therapy with anthracyclines or taxanes for any malignancy

• Cardiopulmonary dysfunction

• Prior malignancies within 5 years prior to randomization, with the exception of those with a negligible risk of metastasis or death and treated with expected curative outcome

• Active or history of autoimmune disease or immune deficiency

• History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest computed tomography (CT) scan

• Urinary outflow obstruction

• Active tuberculosis

• Major surgical procedure other than for diagnosis within 4 weeks prior to initiation of study treatment or anticipation of need for a major surgical procedure during study treatment or within 5 months following the last dose of Atezolizumab (for patients randomized to Atezolizumab)

• Prior allogeneic stem cell or solid organ transplant

• Treatment with systemic immunosuppressive medications within 2 weeks prior to initiation of study treatment or anticipation of need for systemic immunosuppressive medication during the study