Validation of CPS+EG, Neo‐Bioscore, and modified Neo‐Bioscore staging systems after preoperative systemic therapy of breast cancer: Protocol of a retrospective multicenter cohort study in China

Prognostic assessment after preoperative systemic therapy (PST) is critical to develop a therapeutic strategy for breast cancer management. Currently, a clinical–pathologic staging system that incorporates ER status and nuclear grading (CPS + EG), and the Neo‐Bioscore system that includes HER2 status into CPS + EG, are used to predict outcomes in patients with breast cancer after PST. While HER2‐positive is recognized as a favorable factor in the Neo‐Bioscore system based on results in patients administered one year of trastuzumab as anti‐HER2 therapy, most HER2‐positive cases have difficulty accessing anti‐HER2 treatment in China. Therefore, it is crucial that a modified Neo‐Bioscore staging system is developed that incorporates an additional factor of poor prognosis, HER2‐positive status without trastuzumab treatment, to determine accurate prognosis. We propose a retrospective multicenter cohort study in China to validate CPS + EG, Neo‐Bioscore, and the modified Neo‐Bioscore system and determine the accuracy of prediction. Primary breast cancer patients without metastasis treated with PST and surgery in academic institutions or hospitals of provincial level in China will be included. Disease‐free, disease specific, and overall survival will be calculated using the Kaplan–Meier Method, stratified by CPS + EG, Neo‐Bioscore, and the modified Neo‐Bioscore staging system. Areas under the curve of each staging system will be calculated. Multivariate analysis using Wald testing and maximum likelihood estimates in a Cox proportional hazards model will be conducted.