Proliferation rate and breast cancer subtype, but not ALDH1 expression, predict pathological response to neoadjuvant chemotherapy in locally advanced breast cancer.

For locally advanced breast cancer, pathological complete response (pCR) following neoadjuvant chemotherapy (NACT) is associated with good disease-free survival. In several studies, response to chemotherapy according to various parameters has shown strong inter-individual variability. We investigated whether different prognostic factors, including ALDH1 expression, might predict response to NACT in female patients with locally advanced breast carcinoma. ER, PR, Her2/neu, Ki-67 and ALDH1 immunohistochemistry were performed on the initial biopsy and subsequent resection specimens. Residual tumour burden was calculated in post NACT resection specimens using residual cancer burden (RCB) protocol. Of our cohort of 66 patients, 24 (36 %) achieved pCR. Triple negative phenotype and high Ki-67 proliferative index (>40 %) were significantly associated with good response to NACT. ALDH1 expression in tumour epithelial (20 %) or stromal (44 %) cells did not correlate with tumour grade, molecular subtype, proliferative index or NACT response. However, epithelial and stromal ALDH1 expression was significantly increased in residual tumour after NACT. In conclusion, triple negative phenotype and high proliferative index, but not ALDH1 expression, are predictive of good pathological response to NACT. Increased ALDH1 expression following NACT might be associated with a higher probability of recurrent disease.