Concordance of local and central laboratory hormone and HER2 receptor status in ECOG 2197

21022 Background: Central and local laboratory concordance for hormone and HER2 receptor measurement is of national interest. This study compares ER/PR/HER2 by local laboratories using immunohistochemistry (IHC) and central laboratories (IHC & quantitative RT-PCR). Methods: Of 2952 patients in E2197, a case-cohort sample of 776 patients who either did (N=179) or did not recur was studied. Central IHC for ER/PR/HER2 was performed using single 0.6 mm microarrays; Allred score (AS) was used for ER/PR (AS>2 = positive). Positive HER2 was 3+ staining in >10% cells for Central IHC and 2+ or 3+ for Local IHC. RT-PCR analysis by Oncotype DX™ for ER/PR/HER2 was performed using pre-defined cutoffs of 6.5, 5.5 and 11.5 units, respectively. Hormone receptor (HR) pos was defined as ER &/or PR pos. Results: Results from Local IHC (ER/PR in 776 & HER2 in 517 pts) were compared with Central IHC (760 pts) and RT-PCR results (776 pts). The discordance between HR positivity by Local IHC and RT-PCR was very low. However, 12%...