Comparison of ER, PR, HER2 in primary and paired relapsed/metastatic lesions of metastatic breast cancer patients

Abstract

1063 Background: The assessment of ER, PR and HER2 is made routinely in every breast cancer patient to have information about prognosis and to select patients (pts) who are candidates for hormonal and anti-HER2 therapy. Recent studies have shown some degrees of discordance in ER, PR, and HER-2 expression between primary and recurrent/metastatic lesions (RML). In this study we compared the ER, PR, and HER2 status of the primary and paired RML in metastatic breast cancer pts. Methods: Analysis was made on 79 metastatic breast cancer pts whose ER, PR, and/or HER2 status were known both on the tissue samples of primary and RML. ER, PR, and HER2 status were determined by immunohistochemistry and/or fluorescence-in-situ hybridization. Results: Among the RML sites, 24% were locoregional, 76% were distant metastatic sites. Among 72 pts with known ER expression on both primary and RML, 36% showed discordance on ER expression. Most of the change occurred from negative to positive ER status (15 of 48 ER positive primaries had ER negative paired metastasis and 11 of 24 ER negative primaries had ER positive paired metastasis). Among 68 pts with known PR expression on both primary and RML, 51.5% showed discordance on PR expression. Change in PR status from positive to negative and negative to positive was similar (23 of 45 PR positive primaries had PR negative paired metastasis and 12 of 23 PR negative primaries had PR positive paired metastasis). Among 58 pts with known HER2 expression on both primary and RML, 15.5% showed discordance on HER2 expression. Six pts with HER-2 negative primaries, showed HER2 overexpression in their paired RML. Four pts who had HER2 overexpressing primary did not show HER2 expression in the paired RML. Conclusions: A proportion of pts show discordances in hormonal receptor and HER2 expression between the primary tumor and the paired RML. As these discordant results make changes in treatment decision, a biopsy of the metastatic lesion could be recommended in metastatic breast cancer pts when feasible. No significant financial relationships to disclose.