The impact of serum interleukin-17a as a predictive biomarker for neoadjuvant therapy response in breast cancer: a retrospective study.

Background: Breast cancer (BC) is a common and highly malignant disease. Recently, interlukin-17a (IL-17a) was found to be associated with several human malignancies. However, the role of IL-17a in predicting treatment response in BC patients undergoing neoadjuvant therapy (NAT) remains unclear, with limited data exploring its potential as a biomarker. There is a significant clinical need for reliable predictive biomarkers to assist in treatment planning and personalized therapy for BC patients. This study aims to investigate plasma IL-17a expression in BC, and explore its role in disease progression and its interaction with the efficacy of neoadjuvant therapy. Methods: This retrospective cohort study included 54 BC patients who underwent NAT. Inclusion criteria were BC patients receiving standard NAT regimens. Plasma IL-17a expression in BC tissue samples was analyzed via immunohistochemistry. Patients were followed up for a predefined period to assess clinical outcomes and treatment response, measured by pathological complete response (pCR) and radiological assessment, per clinical guidelines. Additional covariates, including tumor stage, histological subtype, and demographics, were recorded and analyzed. Results: The statistical analysis showed that a high expression of IL-17a before and after neoadjuvant therapy was positively correlated with poor responses [i.e., stable disease (SD) and progressive disease (PD)] (P=0.04, P=0.0007). Conversely, compared to those with poor responses, IL-17a was significantly decreased in patients with good responses [i.e., a complete response (CR) and partial response] (P<0.0001). Moreover, IL-17a expression was more decreased in patients with early stage disease (P=0.04). Further, plasma IL-17a was positively trended correlated with a poor prognosis [i.e., progression-free survival (PFS)] after treatment (P=0.09). Conclusions: These findings highlight IL-17A as a dynamic biomarker modulated by NAT, with elevated levels indicating aggressive tumor behavior and resistance to therapy. The significant reduction of IL-17A in responsive patients, especially those with early-stage disease, underscores its potential utility in stratifying patients for personalized treatment. Further large-scale studies are warranted to validate its prognostic role and elucidate mechanisms linking IL-17A to chemoresistance and immune evasion in BC.