HER2 gene amplification (HER2) and hormone receptor expression (ER/PR) in early (EBC) and metastatic breast cancer (MBC) in the same patients

1023 Background: HER2 and ER/PR expression are used as predictors of response to trastuzumab and hormonal treatments, respectively. In most institutions these markers are only analyzed in EBC and any later treatment decisions are based these analyses. At our institution, it has been the routine to verify the breast cancer diagnosis, as well as HER2 and ER/PR status in MBC, if ever possible. We focus this report on data obtained for double testing during the time period 2000–2005. Methods: HER2 and ER/PR in MBC (metastatic site = 43% cutaneous or lymph node; 17% liver; 29% bone, 3% CNS and 8% GI tract) were compared to EBC results. Any result with IHC 3+/FISH amplification was regarded as HER2 +. Any ER/PR expression was regarded as ER/PR +. Results: HER2 testing: We identified sixty one (61) patients who had their tumor analyzed for HER2 in both EBC and MBC. Thirty-seven (61%) of these tumors were negative in both EBC and MBC. One (2%) had a positive EBC and negative MBC; 20 patients (32%) had both positive EBC and MBC testing and 3 patients (5%) had negative EBC testing and positive MBC testing. ER/PR testing: One hundred and four (104) patients underwent both EBC and MBC testing for ER/PR. Forty nine (47%) remained ER/PR +, 7 (7%) had EBC- and MBC+ test; 22 patients (21%) had ER/PR EBC+ test and MBC- test; 26 patients (25%) remained negative from EBC to MBC. Conclusions: Breast cancer tumor characteristics are not constant as the disease progresses. In this study we found that 7% have a change in their HER2 expression and 28% had a change in their ER/PR expression based on analyses of both primary and metastatic disease. It is therefore important that, whenever possible, not only to morphologically verify MBC, but also to analyze HER2 and hormone receptors (ER/PR) to be able to offer the best possible treatment to all patients. [Table: see text]