Evaluation of ALDH1 expression in ipsilateral breast cancer recurrence

Aldehyde dehydrogenase 1 (ALDH1) is a cancer stem cell (CSC) marker that is easily evaluable. The expression and clinical significance of ALDH1 in ipsilateral breast tumor recurrence (IBTR) has yet to be investigated. In the present study, the expression profile of ALDH1 and its correlation with prognosis in IBTR tissues was examined. Patients with IBTR from eight institutions were retrospectively enrolled in the study. Immunohistochemistry was used to examine ALDH1 expression patterns in the tissue specimens of primary cancers and IBTRs. ALDH1 expression levels were investigated in 182 IBTR tumors, which included cases of invasive carcinoma selected from 271 consecutive patients with IBTR. ALDH1 was expressed in 23% of the IBTR tissue samples. The rate of concordant expression between primary cancer and IBTR tissues was 68%. There was no significant association between disease-free survival (DFS) and ALDH1 expression levels in IBTR. IBTRs that expressed ALDH1 and Ki-67 had a poorer prognosis and this expression pattern was significantly associated with DFS (P=0.0073). The percentages of ALDH1 positive expression in each tissue subtype were as follows: Luminal A, 20%; luminal B, 24%; human epidermal growth factor 2 (HER2), 35%; triple-negative, 21%. There was a significant correlation between DFS and ALDH1 expression levels in HER2-type IBTR tissue specimens (P=0.034). In conclusion, it is possible that ALDH1 and Ki-67 expression levels may be useful for predicting prognosis in patients with HER2-type tumors.