Abstract 3752: Folate receptor expression prevalence across multiple tumor types and concordance between matched primary and metastatic tumor pairs

Abstract

Abstract Background: The human folate receptor (FR) is selectively overexpressed in a number of human epithelial malignancies, including ovarian, renal, and prostate cancers. Folate-conjugated therapies provide a strategy for targeting patients with FR expressing tumors. Identification of patients with FR expressing tumors is important to increase the opportunity for clinical benefit from folate conjugated therapies. The goals of this study are to determine the prevalence of FRα expression in various solid tumors, and to determine the concordance of FRα expression between primary and matched metastatic tumors. This concordance could help to determine if primary tumor samples would be suitable for assessing FR expression in metastatic tumors. Little information on this is currently available. Methods: FRα expression was analyzed by immunohistochemistry (IHC) in 339 primary tumors covering a wide range of human tumor types. Concordance of FRα status in 86 archived primary and matched metastatic breast, renal, endometrial and ovarian tumors was assessed by IHC. Results: FRα expression prevalence was moderate to high in primary tumors of lung (13/29; 45%), renal (66/115; 57%), colon (17/27; 63%), prostate (8/12; 67%) and ovarian (22/29; 76%). FRα expression frequency was found relatively low in breast tumor (26/127; 20%) which is consistent with previous reports. Furthermore, for the first time, we showed a good concordance (81.4%) of FRα expression between paired primary and metastatic ovarian, endometrial, renal and breast malignancies. Conclusions: FRα is frequently overexpressed in ovarian, prostate, colon and renal tumors, suggesting these tumor patients might benefit more from folate conjugated therapies. New findings from this study show that FRα expression is maintained in metastatic tumors, indicating the utility of archived primary tumor samples for determining the FR positivity of metastatic tumors in patients receiving a folate conjugated agent. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3752.