In OS analysis, only a Ki67 index ≥20% emerged as an independent prognostic factor (HR = 9.301, <i>p</i> = 0.035), with no statistically significant difference observed for chemotherapy (<i>p</i> = 0.085).<h4>Conclusion</h4>Our findings validate the histological grade and a Ki67 index ≥ 20% as predictive biomarkers of chemotherapy responsiveness in intermediate-risk luminal-subtype breast cancer. Here, MKI67 is linked to breast cancer.