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