Central review of discordant samples for microarray-based ER, PR, and HER2 and local IHC/FISH assessment worldwide from 827 patients.

11 Background: Differences in fixation and IHC and subjective interpretation can substantially affect the accuracy and reproducibility of estrogen receptor (ER), progesterone receptor (PR) and HER2 expression. The commercially available TargetPrint test measures the mRNA expression level of ER, PR and HER2 and is 98% concordant with centrally assessed ER as presented by Viale et al, SABCS 2011. This study compares results from the microarray-based TargetPrint with IHC and FISH (for HER2 IHC2+) generated by local standard procedures. Methods: Fresh tumor samples (core needle biopsies or surgical) were collected for 831 patients diagnosed with breast cancer stage I to IV (Feb 2008 - Jan 2011) from 22 hospitals from Europe, New Zealand, Japan and US. The results of the IHC/FISH assessments performed according to the local standards at the hospitals were compared to the quantitative gene expression readouts with TargetPrint. Discordant cases were centrally reviewed for IHC/FISH assessment. Results: Of the 831...