J Breast Dis.  2026 Jun;14(1):1-8. 10.14449/jbd.2026.14.1.1.

P-STAT3 Expression in Breast Cancer: Clinical Correlations and Limitations as a Prognostic Marker

• Jin H
• Kim HA
• Sung M
• Park C
• Kong J
• Lim D
• Lim H
• Han Y

• KMID: 2582499
• DOI: http://doi.org/10.14449/jbd.2026.14.1.1

Abstract

Purpose
Phosphorylated signal transducer and activator of transcription 3 (p-STAT3) plays a critical role in tumor growth, survival, and immune evasion. Elevated p-STAT3 expression has been reported in breast cancer; however, its prognostic and predictive significance remains controversial. In this study, we aimed to investigate the clinical implications of p-STAT3 expression in breast cancer.
Methods
This retrospective cohort study included 924 patients with invasive breast cancer, excluding 15 patients with de novo stage IV disease. Disease-free survival (DFS) and late recurrence-free survival were analyzed. In addition, dynamic changes in p-STAT3 levels were quantitatively calculated preand post-neoadjuvant chemotherapy and at recurrence, when available.
Results
Kaplan–Meier analysis revealed no significant difference in DFS between the p-STAT3-positive and -negative groups (p=0.875). Subgroup analysis showed that patients with p-STAT3-positive triple-negative breast cancer exhibited a numerically lower late recurrence-free survival, although this did not reach statistical significance (p=0.149). Conversely, in patients receiving neoadjuvant chemotherapy, p-STAT3 expression significantly decreased following treatment (p<0.001).
Conclusion
p-STAT3 expression was not significantly associated with recurrence in breast cancer, including its subtypes. However, its reduction following neoadjuvant chemotherapy suggests that p-STAT3 may reflect dynamic changes in tumor biology during treatment. Long-term follow-up is required to determine its clinical relevance to late recurrence.

Keyword

Breast neoplasms; Disease-free survival; Neoadjuvant therapy; STAT3 transcription factor; Triple negative breast neoplasms