Can a vaccine train the immune system to hunt down hidden breast cancer cells?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

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