A Vaccine (STEMVAC) for Improving Survival in Patients With Triple-Negative Breast Cancer and Moderate or Extensive Residual Cancer Burden

Inclusion Criteria: * At least 18 years of age * Eastern Cooperative Oncology Group (ECOG) performance status score of ≤ 2 * Triple-negative breast cancer as determined by the treating oncologist * Completed standard of care neoadjuvant chemotherapy in the opinion of their treating oncologist * Patients whose tumors progress on neoadjuvant therapy may be enrolled * No clinical evidence of local or distant recurrence * Plan to receive standard of care adjuvant directed therapy * Completed standard of care locoregional treatment, including definitive breast and lymph node surgery followed by standard radiation therapy, if recommended * Residual cancer burden (RCB) index 2 or 3 as calculated per routine anatomic pathology clinical standards * Absolute neutrophil count (ANC) ≥ 800/μL (within 30 days of first study vaccine administration) * Hemoglobin (Hgb) ≥ 8 g/dL (within 30 days of first study vaccine administration) * Platelets ≥ 75,000/ μL (within 30 days of first study vaccine administration) * Total bilirubin ≤ 1.5 x institutional upper limit of normal (ULN), except patients with Gilbert's syndrome, in whom total bilirubin must be \< 3.0 mg/dL (within 30 days of first study vaccine administration) * Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ≤ 1.5 x institutional ULN (within 30 days of first study vaccine administration) * Creatinine ≤ 1.5 x ULN mg/dL or creatinine clearance \> 60 mL/min (within 30 days of first study vaccine administration) * At least 28 days post systemic steroids prior to enrollment, unless used as part of prophylaxis to prevent intravenous (IV) contrast reactions. * Topical, ocular, intra-articular, intranasal, inhalational corticosteroids (with minimal systemic absorption) are allowed * Must have recovered from major infections and/or surgical procedures; and in the opinion of the investigator, not have any significant active concurrent medical illnesses or condition precluding protocol treatment * Patients of child-bearing potential must agree to use dual methods of contraception and have a negative urine pregnancy test at screening, and male patients must use an effective barrier method of contraception if sexually active with a person of child-bearing potential. Acceptable methods of contraception are abstinence, condoms with contraceptive foam, oral, implantable or injectable contraceptives, contraceptive patch, intrauterine device, diaphragm with spermicidal gel, or a sexual partner who is surgically sterilized or post-menopausal Exclusion Criteria: * Toxicities related to prior exposure to immune checkpoint inhibitors for which immune checkpoint inhibitors cannot be safely continued as determined by study investigator * Germline BRCA1 or BRCA2 mutations with adjuvant olaparib planned within the study period * NOTE: If olaparib is not planned, then these patients are eligible * Any known cardiac conditions: * Symptomatic restrictive cardiomyopathy * Dilated cardiomyopathy * Unstable angina within 4 months prior to enrollment * New York Heart Association functional class III-IV heart failure on active treatment * Symptomatic pericardial effusion * Autoimmune disease requiring active systemic treatment * Known hypersensitivity reaction to the GM-CSF adjuvant; any known contra-indication to GM-CSF * Pregnant or breast feeding * Known history of human immunodeficiency virus (HIV) infection, hepatitis B (e.g., hepatitis B virus surface antigen \[HBsAg\] reactive), or hepatitis C (e.g., hepatitis C virus \[HCV\] ribonucleic acid \[RNA\] is detected) * Major surgery within the 4 weeks prior to initiation of first study vaccine * Enrollment in any other clinical protocol or investigational trial that involves concurrent administration of experimental therapy and/or therapeutic devices, or investigational drug. Patients who completed prior clinical trials (such as neoadjuvant treatment, surgery or radiation trials) and are on long term follow up are permitted