Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 within 2 weeks prior to screening

Female and male patients must have histologically confirmed invasive breast cancer that meets the following criteria:

Clinical stage II-III (American Joint Committee on Cancer [AJCC] 7th edition) at diagnosis, based on initial evaluation by clinical examination and/or breast imaging; no metastatic disease allowed

ER- and PR- should meet one of the following criteria:

=< 10% cells stain positive, with weak intensity score (equivalent to Allred score =< 3)

=< 1% cells stain positive, with weak or intermediate intensity score (equivalent to Allred score =< 3)

HER2 negative (not eligible for anti-HER2 therapy) will be defined as:

Immunohistochemistry (IHC) 0, 1+ without in situ hybridization (ISH) HER2/neu chromosome 17 ratio OR

IHC 2+ and ISH HER2/neu chromosome 17 ratio non-amplified with ratio less than 2.0 and if reported average HER2 copy number < 6 signals/cells OR

ISH HER2/neu chromosome 17 ratio non-amplified with ratio less than 2.0 and if reported average HER2 copy number < 6 signals/cells without IHC

NOTE: Patients that originally present with synchronous bilateral tumors are eligible provided both tumors are TNBC, and at least one of them fulfills the remainder eligibility criteria of the protocol; multifocal or multicentric breast cancers are eligible as long as all tumors fulfill eligibility criteria

NOTE: Patients that have a discrepancy in ER/PR/HER2 status between original diagnosis and surgical specimen (if ER/PR/HER2 status were repeated) are not eligible for study participation (i.e. ER/PR/HER2 has to fulfill above criteria in both scenarios)

Patients must have completed neoadjuvant taxane +/- anthracycline; patients must NOT have received cisplatin or carboplatin or capecitabine as part of their neoadjuvant therapy regimen

NOTE: Patients who received preoperative therapy as part of a clinical trial may enroll

NOTE: Patients that were not able to complete their planned neoadjuvant chemotherapy for any reason (i.e. toxicities, etc.) are eligible to participate as long as no further systemic standard of care therapy is planned by the treating physician

Must have completed definitive resection of primary tumor

Negative margins for both invasive and ductal carcinoma in situ (DCIS) are desirable, however patients with positive margins may enroll if the treatment team believes no further surgery is possible and patient has received radiotherapy; patients with margins positive for lobular carcinoma in situ (LCIS) are eligible

Either mastectomy or breast conserving surgery (including lumpectomy or partial mastectomy) is acceptable

Sentinel node biopsy either pre or post neoadjuvant chemotherapy (i.e. at the time of definitive surgery) are allowed; axillary dissection is encouraged in patients with lymph node involvement, but is not mandatory

Post neoadjuvant chemotherapy, patients must be found to have residual invasive cancer in the breast at the time of definitive surgery; residual cancer is defined as a contiguous focus of residual invasive cancer, in the breast, measuring >= 1 cm in diameter, and with more than minimal cellularity, as per local pathologist determination; this is required due to constraints in deoxyribonucleic acid (DNA) extraction for PAM50 analysis

NOTE: The presence of ductal carcinoma in situ (DCIS) without invasion does not qualify as residual invasive disease in the breast

NOTE: Despite lymph node involvement if residual invasive cancer in the breast is < 1 cm in diameter patients are not eligible for participation

Radiotherapy may be given before or after protocol treatment per standard of care guidelines; when radiotherapy is planned prior to protocol treatment administration, patients may be registered and screened while receiving radiation

Post-mastectomy radiotherapy is required for all patients with the following:

Primary tumor >= 5 cm (prior to neoadjuvant chemotherapy [clinically] or at the time of definitive surgery) or involvement of 4 or more lymph nodes at the time of definitive surgery

For patients with primary tumors < 5 cm or with < 4 involved lymph nodes prior to neoadjuvant chemotherapy and at the time of definitive surgery, provision of post-mastectomy radiotherapy is at the discretion of the treating physician

Radiation of regional nodal basins is at the discretion of the treating radiation oncologist

NOTE: Breast radiotherapy (whole breast or partial) is required for patients who underwent breast-conserving therapy, including lumpectomy or partial mastectomy

Hemoglobin (Hgb) > 9.0 g/dL

Platelets > 100,000 mm^3

Absolute neutrophil count (ANC) > 1500 mm^3

Calculated creatinine clearance of > 50 mL/min using the Cockcroft-Gault formula

Bilirubin =< 1.5 x ULN upper limit of normal (except in patients with documented Gilbert?s disease, who must have a total bilirubin =< 3.0 mg/dL)

Aspartate aminotransferase (AST, serum glutamic oxaloacetic transaminase [SGOT]) =< 2.5 x upper limit of normal (ULN)

Alanine aminotransferase (ALT, serum glutamate pyruvate transaminase [SGPT]) =< 2.5 x ULN

Patients with active >= Common Terminology Criteria for Adverse Events (CTCAE) version (v.) 4 grade 2 neuropathy are ineligible

Adjuvant chemotherapy after surgery other than that specified in this protocol is not allowed; luteinizing hormone-releasing hormone (LHRH) agonists and adjuvant bisphosphonate or denosumab use is allowed

Patients must have archived formalin-fixed paraffin-embedded (FFPE) tumor tissue specimen from the residual disease on the definitive surgical specimen available for PAM50 analysis for stratification

Tumor tissue specimen from the definitive surgery has been collected and is ready to ship to the ECOG-American College of Radiology Imaging Network (ACRIN) Central Biorepository and Pathology Facility (CBPF) within 21 weeks post-surgery

The Molecular Diagnostics Laboratory (MDL) at MD Anderson Cancer Center will perform the PAM50 analysis and notify the ECOG-American College of Radiology Imaging Network (ACRIN) operations office within three (3) weeks of receipt of the tumor tissue specimen via secure electronic messaging to the ECOG-ACRIN database; results will not be reported to the submitting institution

NOTE: Tissue must be submitted any time during screening period, even if patient is getting radiation

NOTE: Every effort should be made to submit the tumor tissue specimen to the ECOG-ACRIN CBPF immediately

History of TNBC invasive breast cancer within 5 years of enrollment, no concurrent malignancies of any sort

Clinically significant infections as judged by the treating investigator

ELIGIBILITY CRITERIA FOR RANDOMIZATION (STEP 1):

No specific timeframe between registration and randomization needs to be observed, as long as:

Patients randomized to the chemotherapy arms have their cycle 1/ day 1 (platinum based or capecitabine) start within 3 weeks (15 working days) following randomization date

Randomization occurs no more than 24 weeks from surgery date

Must have PAM50 analysis by digital mRNA quantitation on the formalin-fixed paraffin-embedded tumor tissue specimen (FFPE) of the residual disease in the breast or axilla resected at the time of definitive surgery completed

ECOG performance status 0 or 1 within 2 weeks prior to randomization

Radiotherapy may be given before or after protocol treatment. when radiotherapy is planned prior to protocol treatment administration, patients must have completed adjuvant radiotherapy >= 2 weeks prior to randomization for protocol therapy, if applicable

Patients must have completed treatment with any investigational agent >= 30 days prior to randomization for protocol therapy, if applicable

Patients must be randomized within 24 weeks from surgery

Women must not be pregnant or breast-feeding; all females of childbearing potential must have a blood test or urine study within 2 weeks prior to randomization to rule out pregnancy

A female of childbearing potential is any woman, regardless of sexual orientation or whether they have undergone tubal ligation, who meets the following criteria: 1) has not undergone a hysterectomy or bilateral oophorectomy; or 2) has not been naturally postmenopausal for at least 24 consecutive months (i.e., has had menses at any time in the preceding 24 consecutive months

Women of childbearing potential and sexually active males must be strongly advised to use an accepted and effective method of contraception or to abstain from sexual intercourse for the duration of their participation in the study

Hemoglobin (Hgb) > 9.0 g/dL

Platelets > 100,000 mm^3

Absolute neutrophil count (ANC) > 1500 mm^3

International normalized ratio (INR) =< 3 (to be done/tested only for subjects on warfarin)

Calculated creatinine clearance of > 50 mL/min using the Cockcroft-Gault formula

Bilirubin =< 1.5 x ULN (except in patients with documented Gilberts disease, who must have a total bilirubin =< 3.0 mg/dL)

Aspartate aminotransferase (AST, SGOT) =< 2.5 x ULN

Alanine aminotransferase (ALT, SGPT) =< 2.5 x ULN

• Obstetrics and Gynecology

• Oncology (Adult)

• ECOG-ACRIN Cancer Research Group