Background. Assessing indications for adjuvant chemotherapy (CT) in patients with hormone receptor (HR)- positive/human epidermal receptor 2 (HER2)-negative breast cancer remains a challenge for oncologists. In this study, we evaluated whether forkhead-box protein A1 (FOXA1) expression was a prognostic and predictive marker for HR-positive breast cancer. Methods. FOXA1 expression was analyzed immunohistochemically in 239 primary breast cancers. Associations between FOXA1 expression and clinicopathological characteristics and prognosis were evaluated. Results. FOXA1 expression was positively correlated with estrogen receptor (ER) (P<0.0001) and progesterone receptor (PR) expression (P = 0.0011), and inversely correlated with nuclear grade (P = 0.0048) and Ki67 index (P = 0.0112). High FOXA1 was associated with longer recurrence-free survival (RFS) in all cases (P<0.0001) and in ER-positive cases (P\0.0001), but not in ERnegative cases. In addition, FOXA1 expression was associated with good prognosis, regardless of the Ki67 index, in HR-positive cases. FOXA1 was an independent prognostic factor on multivariate analysis in all cases and in ERpositive cases. Among HR-positive/HER2-negative cases with high FOXA1 expression, there was no difference in RFS between those given hormone therapy (HT) alone and those given CT plus HT. Conclusions. In HR-positive breast cancer, FOXA1 expression was significantly associated with good prognosis. FOXA1 expression may be a useful marker for HRpositive/ HER2-negative breast cancer to identify patients with good prognosis who may not require CT.
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