Prognostic Value of Ki-67 and Progesterone Receptor for Risk Stratification and Outcomes by Adjuvant Chemotherapy in Early Luminal-Type Breast Cancer

Purpose: Risk stratification of hormone receptor-positive (HR+)/HER2-negative early breast cancer remains variable across studies. We aimed to develop and validate an immunohistochemistry (IHC)-based stratification framework (PR10/Ki20) and a quantitative risk score (RS), and to explore clinical outcomes according to receipt of adjuvant chemotherapy (CT). Methods: was derived incorporating PR10/Ki20 categories, age, pathological T stage, and lymphovascular invasion. Results: groups with significantly different DFS in both cohorts (KMTTH: P = 0.005; KMUH: P = 0.004). Conclusion: provide reproducible prognostic stratification in HR+/HER2- early breast cancer across two cohorts. In this retrospective analysis, CT use was associated with improved DFS among patients classified as high risk, while no statistically significant association was observed in the low-risk group. These findings may help inform risk-adapted discussions and generate hypotheses for prospective validation regarding treatment selection.