Although research has linked pre-existing intratumoral immune response—characterized by presence of tumor-infiltrating lymphocytes or cytotoxic effector T cells—with improve prognosis in early triple-negative breast cancer (eTNBC) but suggest that immune-rich tumors are not prognostic in metastatic TNBC (mTNBC), whether the T-cell immune biology has differential prognosis between eTNBC and mTNBC remains unclear, as different immune biomarkers were used across studies to make these observations. For a study, researchers evaluated the prognostic value of the T effector RNA gene signature (Teff), across two eTNBC and two mTNBC clinical studies using the same biomarker methodology. Although Teff levels were similar within the eTNBC studies and within the mTNBC studies, Teff score was significantly higher in the eTNBC studies. Among baseline prognostic characteristics assessed, lymph node involvement in the eTNBC studies was the only one associated with Teff. Multivariate analysis found elevated Teff to be associated with improved overall survival in two eTNBC studies but to have no prognostic value in two mTNBC trials. Similar results were seen at various Teff cutoffs.