Oncotype Dx in PR-negative tumors in light of the prognostic value of PR expression.

e11092 Background: It was suggested that breast tumors that are ER positive / PR negative carry a worse prognosis than ER /PR positive tumors if treated only by adjuvant hormonal therapy. Most studies did not account for HER 2 expression. PR was assessed by methods that measure protein content. Oncotype Dx measures mRNA expression. In clinical trials the discrepancy between IHC and RT PCR for the expression of PR was about 20%, but this was not assessed in a community setting. The meaning of a high level of mRNA without detectable PR protein is unclear and might be due to technical issues or a biological mechanism such as translational inhibition by miRNA's. We sought to verify the prognostic value of the expression of the progesterone receptor by IHC in women with early stage HER 2 negative, ER positive BC treated with systemic hormonal therapy only and to characterize the results of Oncotype Dx in ER positive, PR negative HER 2 negative tumors. Methods: An historical prospective analysis of patients fil...