Folate Receptor Alpha Expression Is Associated With Increased Risk of Recurrence in Triple-negative Breast Cancer.

Background: Folate receptor alpha (FOLR1) has been identified as a potential prognostic and therapeutic target in breast cancer. The limited studies evaluating the role of FOLR1 in breast cancer have shown that FOLR1 protein expression is enriched in triple-negative breast cancer (TNBC) and associated with poor prognosis in all breast cancer types. Newly developed anti-FOLR1 therapy could potentially be used in patients with TNBC for whom few therapeutic options exist. We sought to evaluate FOLR1 protein expression in a cohort of patients with TNBC to determine its prevalence and prognostic value.

Materials: Immunohistochemistry was performed for FOLR1 in 76 cases of primary TNBC. Membranous staining in ≥ 5% of cells was deemed positive in a given case. Statistical analyses correlating FOLR1 protein expression with clinicopathologic parameters and clinical outcome (disease-free survival and overall survival) were performed.

Results: A total of 76 cases of primary TNBC were studied. Most cases were negative for FOLR1 (80.3%; 61/76). FOLR1 expression did not correlate with any clinicopathologic parameters. FOLR1 expression was significantly correlated with decreased disease-free survival (hazard ratio, 2.61; 95% confidence interval, 0.96-7.09; P = .0497 log-rank test). Although FOLR1 expression trended towards decreased overall survival, it was not statistically significant (hazard ratio, 1.99; 95% confidence interval, 0.62-6.36; P > .05 log-rank test).

Conclusion: We found a lower incidence of FOLR1 expression in TNBC compared with other studies; however, these patients may benefit from anti-folate therapy as other targeted therapies are not available. Although no correlation between FOLR1 expression and standard clinicopathologic parameters was identified, our findings suggest that FOLR1 expression is prognostically significant in TNBC.