Evaluating Biomarker Dynamics in Breast Cancer Post-Neoadjuvant Chemotherapy: A Retrospective Cross-sectional Study

Background: Neoadjuvant chemotherapy (NACT) is integral to breast cancer management, yet its influence on biomarkers, notably androgen receptor (AR), remains underexplored. This study examines post-NACT alterations in receptor status, including ER, PR AR, HER2 and Ki67 index in breast cancer patients. Methods: A cross-sectional study, spanning three years at a tertiary care center, enrolled patients with invasive breast cancer undergoing mastectomy post-NACT. Pre- and post-NACT specimens underwent histological grading and immunohistochemistry for hormone status, HER2 status, and Ki67 index. Discordance between pre- and post-NACT receptor statuses and expression levels of biomarkers was assessed using McNemar’s and Wilcoxon signed rank tests respectively. Results: Among 100 patients, 35 were assessed. Mean age was 43.83 years, with prevalent T1 tumors (34.3%) and N1 nodal involvement (37.1%). Post-NACT, 54.2% showed no histological grade change. Notable alterations included changes in ER (14.2%), PR (14.2%), and HER2 status (8.57%). AR expression showed a significant change following NACT (p=0.03), while ER expression exhibited a trend towards significance (p=0.06). Ki67 index decreased in only 5.7% of cases. Conclusion: This study unveils intricate biomarker dynamics following NACT in breast cancer, with particular emphasis on AR, hitherto not evaluated. Larger investigations are imperative to elucidate clinical implications and tailor treatment strategies for breast cancer patients undergoing NACT.