PURPOSE: breast cancer is common and highly malignant, currently, STMN1 was found to be associated with several human malignancies. The purpose of this study is to investigate STMN1 expression in breast cancer and explore its role in disease progression and its interaction with neoadjuvant therapy efficacy. METHODS: we analyzed the tissue STMN1 mRNA expression in BC tissue samples from 105 patients received with neoadjuvant therapy using qPCR between 2019 and 2022. RESULTS: Statistical analysis showed that a high expression of STMN1 before neoadjuvant chemotherapy (NACT) was a trend positively related to non-pCR in the ITT (Intention to Treat) population, while in patients with paclitaxel or docetaxel regimens, before-NACT STMN1 expression was obviously higher in non-pCR (failure to achieve pathologically complete response) patients. Additionally, compared to pCR, high expression of STMN1 after NACT was obviously related to non-pCR. Interestingly, Kaplan-Meier analysis demonstrated that patients with mid-high STMN1 expression before and post-NACT had a poorer PFS to compared to those with low expression. CONCLUSIONS: STMN1 is the potential biomarker of NACT and prognosis for breast cancer.