PURPOSE: Most estrogen receptor (ER)-positive breast cancer responds poorly to 
chemotherapy and no single cost-effective biomarker capable of selecting 
chemosensitive ones has been found yet. We investigated FOXA1 for its role in 
predicting chemosensitivity of this subgroup in neoadjuvant chemotherapy 
settings.
METHODS: We reviewed pathologic slides of 123 patients who were diagnosed with 
ER-positive breast cancer on core needle biopsy and underwent neoadjuvant 
chemotherapy at our institution between 2002 and 2012. FOXA1 expression and 
pathologic response were evaluated. We then statistically analyzed FOXA1 
expression and its relationship with chemosensitivity.
RESULTS: FOXA1 expression before NAC was correlated with poor chemoresponse in 
ER-positive as well as luminal A and luminal B breast cancer patients (p = 
0.002, 0.001, and 0.049 respectively). Significant association between change of 
FOXA1 staining position after NAC and chemosensitivity also was observed (p = 
0.024). Multivariate analysis identified FOXA1 expression before NAC as an 
independent predictor of chemosensitivity in ER-positive and luminal A breast 
cancer patients [p = 0.002; relative risk (RR) 0.163; 95 % confidence interval 
(CI) 0.053-0.500, and p = 0.002; RR 0.055; 95 % CI 0.008-0.353, respectively]. 
Additionally, change of FOXA1 staining position after NAC was shown to be an 
independent predictor of chemoresponse in luminal B subtype breast cancer 
patients (p = 0.012; RR 0.153; 95 % CI 0.035-0.665).
CONCLUSIONS: FOXA1 expression can independently predict chemosensitivity of 
ER-positive breast cancer patients.