Homologous Recombination Repair Status as a Biomarker of Response in Locally Recurrent/Metastatic Triple Negative Breast Cancer Patients Treated With Concurrent Cisplatin and Radiation Therapy

Inclusion Criteria: * Histologically-confirmed invasive triple negative breast cancer (ER \<1%, PR \<1%, her-2-neu 0-1+ by IHC or FISH-negative) or as determined by MD discretion * Radiation to the recurrent or metastatic site is clinically indicated and would be considered standard care for palliation or for locoregional control * Age ≥18 years * Tumor to be irradiated is measurable by RECIST 1.1 or PRC * Willingness to undergo tumor biopsy prior to initiation of treatment * Life expectancy greater than 6 months * ECOG performance status 0-2 * Any prior chemotherapy is allowed including prior treatment with platinum-containing chemotherapy * Prior treatment with FDA-approved or investigational biologics or novel molecularly target therapies, including oral or IV formulations, are permitted. * Patients must be off prior targeted therapy for at least 14 days prior to study biopsy. * Use of an effective means of contraception in women of child-bearing potential * Ability to comprehend and sign informed consent * Adequate organ and marrow function within 14 days prior to study entry, defined as: * Absolute neutrophil count (ANC)\>1000/mm3 * Hemoglobin \>9 gm/dl * Platelets \>100,000/mm3 * Serum creatinine \<1.5 mg/dl OR creatinine clearance of ≥ 50 cc/min * SGOT/SGPT\<2.5X institutional ULN (\<5X ULN if known liver metastases) Exclusion Criteria: * Unmeasurable target tumor site by RECIST 1.1 or PRC (ex: lesions \<2 cm on CT or MR scan, leptomeningeal disease, ascites, pleural/pericardial effusion, lymphangitis, non-FDG-avid skin lesions) * Brain metastases requiring focal or whole brain radiation will be excluded, as these lesions cannot be biopsied and can have life expectancies \<6 months. * Inability to obtain a biopsy of the tumor as deemed by the study Interventional Radiologist * Prior chemotherapy completed \<7 days prior to planned study entry * Prior RT is allowed and must have been completed more than 7 days before planned study entry. * Note: For re-irradiation cases, standard departmental guidelines should be followed so as to not exceed normal tissue * Life expectancy less than 6 months * Intercurrent illness or other major medical condition or comorbid condition that might affect study participation (uncontrolled renal, pulmonary or hepatic dysfunction or infection) * Renal dysfunction for which cisplatin dose would be considered unsafe. * Women on study must be neither pregnant nor nursing nor expected to become pregnant during therapy. For premenopausal women, negative pregnancy test within 14 days of RT is required. * Concurrent active malignancy other than non-melanomatous skin cancer or carcinoma in-situ of the cervix, unless treatment for the previous cancer was completed \>2 years prior to study entry and patient has remained disease-free.