Atezolizumab + Sacituzumab Govitecan to Prevent Recurrence in TNBC (ASPRIA)

Inclusion Criteria: * Pathologically confirmed residual invasive breast cancer, in the breast and/or lymph node(s), following neoadjuvant chemotherapy. In the absence of residual invasive disease in the breast, lymph node must contain at least 2mm of invasive disease. * HER2 negative in primary tumor pre-treatment by local pathology assessed according to current ASCO/CAP guidelines: * In situ hybridization non-amplified (ratio of HER2 to CEP17 \< 2.0 or single probe average HER2 gene copy number \< 4 signals/cell), OR * Immunohistochemistry (IHC) 0 or IHC 1+. * NOTE: If more than one test result is available and not all results meet the inclusion criterion definition, all results should be discussed with the Principal Investigator to establish eligibility * ER and PR negative in primary tumor pre-treatment defined as \< 10% of cells expressing hormonal receptors via IHC analysis by local laboratory assessment. * Patients must have received neoadjuvant chemotherapy prior to breast surgery. * Patients must be within 4 months of completion of all locoregional therapy (either last surgery or last dose of radiation, whichever is later) . Definitive breast surgery must have been performed and includes lumpectomy or mastectomy with pathologically clear margins (i.e. no ink on tumor). For patients undergoing lumpectomy, this must be followed by whole breast irradiation. Definitive surgery also includes axillary surgery, either sentinel lymph node biopsy or axillary lymph node…