Impact of the mode of estrogen receptor determination on breast cancer prognosis

e11609 Background: Impact of the mode of estrogen receptor determination on breast cancer prognosis Abstract Background: We examined if the mode of estrogen receptor (ER) determination and expression in primary breast cancer impact on patient's prognosis. Methods: We conducted an analysis on a prospective cohort of 1012 patients treated for stage I-III Breast Cancer at Conception Hospital, Marseille, France between 1984 to 2003. ER was determined according to enzyme immuno-assay (EIA) and immunohistochemistry (IHC). Disease-free and overall survivals were evaluated according to the mode of ER quantification and in function of qualitative or quantitative ER expression. Results: ER was a strong predictor of overall survival in the whole population whatever method used for the status determination (p<0.001); however when stratifying the analysis on ER quantitative expression, ER was still a prognostic indicator in the EIA group for OS (p= 0.004) and DFS (p<0.001), group but not in the IHC group for OS (p=0.58) and DFS (p= 0.195). Conclusions: ER determination in breast cancer is strongly associated with a better prognosis, but the level of influence of ER varies with the assay and ER expression. No significant financial relationships to disclose.