Patients must be offered the opportunity to participate in specimen banking;

The BAHO substudy was permanently closed to accrual on June 23, 2020, and willingness of English-speaking patients to participate in the BAHO substudy is no longer applicable;

Patients must have had neoadjuvant chemotherapy followed by surgery; the choice of neoadjuvant chemotherapy is determined by the treating physician; we recommend following the National Comprehensive Cancer Network (NCCN) treatment guidelines for TNBC; patients who cannot complete all planned treatment cycles for any reason are considered high risk and therefore are eligible for the study if they have residual disease; patients must have resolution of adverse event(s) of the most recent prior chemotherapy to grade 1 or less, except alopecia and =< grade 2 neuropathy which are allowed;

Patients must be >= 18 years of age;

Patients must have Zubrod performance status =< 2

Patients must not have metastatic disease (i.e., must be clinically M0 or Mx; systemic staging studies with imaging should follow routine practice as per National Comprehensive Cancer Network [NCCN] and ASCO guidelines); patients must not have locally recurrent disease;

Patients must not have had prior immunotherapy with anti-PD-L1, anti-PD-1, anti-CTLA4 or similar drugs; patients must not be planning to receive any of the prohibited therapies during the screening or treatment phases of the study;

Patients must not be planning to receive concomitantly other biologic therapy, hormonal therapy, other chemotherapy, surgery or other anti-cancer therapy except radiation therapy while receiving treatment on this protocol; however, patients receiving extended adjuvant endocrine therapy for an earlier ER positive breast cancer treated with curative intent and without recurrence for at least 5 years may continue with their endocrine therapy; elective surgery or surgery that is not related to cancer therapy is allowed, at the discretion of the treating investigator;

Patients must not have a history of (non-infectious) pneumonitis that required steroids or evidence of active pneumonitis within 2 years prior to registration;

Patients must not have active autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs); replacement therapy (e.g., thyroxine for pre-existing hypothyroidism, insulin for type I diabetes mellitus, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment

• Obstetrics and Gynecology

• Oncology (Adult)

• National Cancer Institute (NCI)