ERBB2 and breast carcinoma: When direct costs for systemic treatment are analyzed according to the stage and biological profile of breast cancer (hormone-sensitive, human epidermal growth factor receptor 2 [HER2]–positive, HER2-negative, or triple-negative), it is observed that for HER2-negative breast cancer, the stage IV treatment reaches 6,368 USD per patient, doubling the cost of treating patients with stage IIB-III and tripling that of those with stage IA and IIA.