HER2 concordance between central laboratory immunohistochemistry and quantitative reverse transcription polymerase chain reaction in Intergroup Trial E2197

22009 Background: Laboratory assessment of HER2 is of marked clinical importance. Accurate quantification remains problematic within and between laboratories. Here we report central laboratory HER2 results comparing IHC and quantitative RT-PCR using Oncotype DX in patients enrolled in a large adjuvant breast cancer trial. Methods: 755 patients with 0 to 3 positive lymph nodes from Intergroup study E2197 were studied. Central IHC for HER2 was performed using duplicate 1.0 mm microarrays (HercepTest; Dako). Percent positive cells and staining intensity (0–3+) was assessed, where IHC positive cases exhibited 3+ staining in >30% cells, IHC equivocal cases exhibited 3+ staining in 10.7-<11.5 units, and negative ≤10.7 units (each unit represents a 2-fold change in expression). Concordance analysis excluded the equivocal range from b...