Predicting Response of Metastatic Triple Negative Breast Cancer to Immunotherapy Based on Patients Cytokine Profile

This is a prospective study that has two groups of patients as determined by their prescribed treatment plan. Group A (control group) are patients with metastatic triple-negative breast cancer (TNBC) who receive chemotherapy only (current standard of care). Group B (experimental group) are patients with mTNBC who receive a combination of chemotherapy and IT immunotherapy (Atezolizumab) which is a standard of care for patients whose tumor express \>1% of PD-L1 molecules. T-cell cytokines will be measures prior to treatment and at multiple time points during the treatment.