Study of Tislelizumab Plus Chemotherapy vs Chemotherapy as Perioperative Treatment in Participants With HER2 Negative Breast Cancer

Inclusion Criteria: * Pathologically proven diagnosis of invasive breast cancer, cT1-T3, cN0-N3, cM0, HR+ (ER+ and/or PR+) HER2 negative or HR- (ER- and PR-) HER2 negative/triple negative breast cancer. * Provides a core needle biopsy consisting of at least 2 separate tumor cores from the primary tumor at screening to the central laboratory. * Immune active subtype revealed by multiplexed * Has Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 performed within 10 days of treatment initiation. * Demonstrates adequate organ function. Exclusion Criteria: * Has a history of invasive malignancy ≤5 years prior to signing informed consent except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer. * Has received prior chemotherapy, targeted therapy, or radiation therapy for breast cancer. * Has received prior therapy with an anti-programmed cell death protein 1 (anti-PD-1), anti-programmed death - ligand 1 (anti-PD-L1), or anti-PD-L2 agent or with an agent directed to another co-inhibitory T-cell receptor (e.g. CTLA-4, OX-40, CD137) * Has an active autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs). * Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy (i.e. dosing exceeding 10 mg daily of prednisone or equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study treatment. * Has a known history of Human Immunodeficiency Virus (HIV). * Has known active Hepatitis B or Hepatitis C. * Has a known history of active tuberculosis. * Has a history of (non-infectious) pneumonitis that required steroids or current pneumonitis. * Has an active infection requiring systemic therapy. * Has significant cardiovascular disease, such as: history of myocardial infarction, acute coronary syndrome or coronary angioplasty/stenting/bypass grafting within the last 6 months OR congestive heart failure (CHF) New York Heart Association (NYHA) Class II-IV or history of CHF NYHA Class III or IV. * Pregnant or lactating women are ineligible.