Changes in PgR and Ki-67 in residual tumour and outcome of breast cancer patients treated with neoadjuvant chemotherapy

Background: Limited data are available on the prognostic value of changes in the biological features of residual tumours following neoadjuvant therapies in breast cancer patients. Patients and methods: We collected information through the institutional clinical database on all consecutive breast cancer patients treated with neoadjuvant chemotherapy at the European Institute of Oncology (IEO), Milan, Italy, between 1999 and 2011. We selected patients who did not achieve pathological complete response at final surgery. All patients had a pathological evaluation, including ER, PgR, HER2 protein and Ki-67 expression carried out at the IEO both at diagnostic core biopsy and at final surgery. Results: We identified a total of 904 patients. The 5% of patients who were ER positive at diagnostic biopsy had ER-negative residual tumour at final surgery. For PgR expression, 67% of the patients, whose tumours had a PgR > 20% at diagnostic biopsy had a PgR < 20% at final surgery. The Ki-67 expression changed from > 20% to < 20% in 40% of the patients. At the multivariate analysis, the decrease of PgR-immunoreactive cells correlated with improved outcome in terms of disease-free survival (DFS) [hazard ratio (HR) 0.73; 95% confidence interval (CI) 0.54-1.00, P 0.046]. In addition, the decrease of Ki-67 expression to < 20% of the cells at final surgery was found to be associated with better outcome both in terms of DFS (HR 0.52; 95% CI 0.40-0.68 P < 0.0001) and overall survival (HR 0.45; 95% CI 0.32-0.64, P < 0.0001). Conclusion: The decrease of PgR and Ki-67 expression after preoperative chemotherapy has a prognostic role in breast cancer patients with residual disease.