High FOXA1 protein expression might predict late recurrence in patients with estrogen-positive and HER2-negative breast cancer.

Background: Multi-gene expression assays have been developed with the aim of predicting late recurrence in patients with estrogen receptor (ER)-positive breast cancer. However, establishment of alternative markers based on immunohistochemistry is also important for achieving practical use. Based on our previous study, forkhead box A1 (FOXA1) protein was tested as a potentially useful predictive marker for late recurrence.

Methods: 117 patients with ER-positive HER2-negative invasive breast cancer who developed distant metastasis following curative surgery were retrospectively investigated. We also evaluated responsiveness to endocrine therapy according to FOXA1 expression. Furthermore, publicly available mRNA microarray data were analyzed to examine patterns of metastasis according to FOXA1 mRNA expression, employing the Kaplan-Meier plotter.

Results: High expression of FOXA1 was an independent factor predicting long disease-free survival (DFS), along with small tumor size (p = 0.010 and 0.016, respectively). Discrimination of DFS was improved by combining these two factors, i.e., patients with FOXA1-high small tumors had the longest DFS while those with FOXA1-low large tumors had the shortest DFS. Moreover, we revealed that risk of distant metastasis started to increase after the completion of adjuvant endocrine therapy in patients with FOXA1-high tumors.

Conclusion: Among patients who developed distant metastasis, those with FOXA1-high tumors had significantly longer DFS. We believe our data to raise the possibility of FOXA1 being a useful predictive marker for late recurrence and to provide new insights into the biology of FOXA1-high breast cancers.