Folate receptor overexpression is associated with poor outcome in breast cancer

The high affinity folate receptor is a membrane-associated glycoprotein that is preferentially expressed in cancers of epithelial origin and rarely expressed in normal cells. We examined its expression pattern in breast cancer, utilizing a tissue microarray containing samples from 63 invasive breast cancers from women with divergent clinical outcomes. Thirty-three women comprised the poor outcome group with a median time to recurrence of 1.9 years. Thirty women, the good outcome group, were free of recurrence for a minimum of 7 years after diagnosis. The intensity of folate receptor staining was strongly correlated with outcome. There were two summary categories of staining intensity: weak (n = 42) or strong (n = 21). In the strong staining group, 17 of 21 women (81%) have recurred and their median survival is 2.4 years. In the weak staining group, 16 of 42 women (38%) have recurred. Their median survival is not estimable. After adjustment for tumor size, nodal status, ER status, adjuvant therapy, histology and tumor grade, strong staining for the folate receptor remained significantly associated with poor outcome, p < 0.001. Our work requires validation in a larger cohort, but supports the possibility of using folate receptor-targeted approaches in the management of breast cancer. (C) 2007 Wiley-Liss, Inc.