Abstract P4-12-14: Folate receptor alpha (FOLR1) expression in triple-negative breast cancer (TNBC)

Abstract 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). Newly developed anti-FOLR1 therapy could potentially be used for 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. Design Immunohistochemistry was performed for FOLR1 (26B3.F2, Biocare, RTU) on tissue microarray (TMA) slides consisting of 62 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 (DSF) and overall survival (OS) (range: 16 to 196 months, mean: 111 months)] were performed. Results 62 cases of primary TNBC from 61 patients were studied. All patients were female and the mean age was 55 years (range 30 to 91 years). Histologically, almost all tumors were invasive ductal carcinoma (94%; 58/62) and grade 3 (89%; 55/62). Most were pT1 tumors (71%; 44/62) or pT2 (27%; 17/62). For the majority of patients, the nodal status was N0 (61%; 38/62) or N1 (24%; 15/62) and the stage was 1 (53%; 33/62) or 2 (32%; 20/62). Most cases were negative for FOLR1 (84%; 52/62). FOLR1 expression did not correlate with any clinicopathologic parameters, DFS or OS (P>0.05). Conclusion Similar to other studies, we found no correlation with FOLR1 expression and common clinicopathologic parameters and clinical outcome in TNBC. While FOLR1 expression has been previously reported to confer poor prognosis in breast cancer (all types), our findings suggest that in TNBC specifically, FOLR1 expression is not prognostically significant. Citation Format: Cui X, McIntire PJ, Ginter PS, Irshaid L, Chen Z, Shin SJ. Folate receptor alpha (FOLR1) expression in triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-14.