Ki-67 Dynamics and Biomarker Conversion as Prognostic Factors in Residual Breast Cancer

Area of Science:

• Oncology
• Breast Cancer Research
• Translational Medicine

Background:

• Neoadjuvant chemotherapy (NAC) can alter tumor biomarkers (ER, PR, HER2) in residual breast cancer.
• Receptor conversion post-NAC raises questions about prognostic significance and adjuvant therapy guidance.
• The prognostic impact of biomarker conversion versus proliferative dynamics (Ki-67) is debated.

Purpose of the Study:

• To investigate the prognostic weight of biomarker conversion and Ki-67 dynamics in patients with residual breast cancer post-NAC.
• To determine if changes in ER, PR, and HER2 status after NAC affect survival outcomes.
• To identify key factors for risk stratification and adjuvant therapy decisions.

Main Methods:

• Retrospective analysis of 338 invasive breast cancer patients with residual disease after NAC and surgery.
• Paired assessment of ER, PR, HER2, and Ki-67 status (pre-NAC vs. post-NAC).
• Survival outcomes (DFS, OS) analyzed using Cox regression, with adjuvant therapy adapted to post-NAC IHC profile.

Main Results:

• Substantial biomarker conversion rates observed: ER (13.9%), PR (18%), HER2 (27%).
• Biomarker status changes did not significantly impact disease-free survival (DFS) or overall survival (OS).
• Ki-67 dynamics were a significant independent prognostic factor; low Ki-67 post-NAC correlated with superior DFS and OS.

Conclusions:

• Biomarker conversion in residual breast cancer is common but does not worsen survival if adjuvant therapy is tailored to post-NAC IHC results.
• Tumor proliferative response, indicated by Ki-67 levels, is the predominant driver of prognosis.
• Persistent high Ki-67 should guide escalation of adjuvant therapy and risk stratification over biomarker conversion.