For all underlying models estimating the mortality risk for stage I, we selected the following predictive variables: age, location within the breast, tumor differentiation grade, histological tumor type, multifocality, hormonal receptor status (ER/PR status), HER2 status, type of surgery, axillary lymph node dissection, use of adjuvant systemic therapy, primary systemic therapy, targeted therapy and radiotherapy. Here, ERBB2 is linked to neoplasm.