NanoString nCounter® Approach in Breast Cancer: A Comparative Analysis with Quantitative Real-Time Polymerase Chain Reaction, In Situ Hybridization, and Immunohistochemistry.

Purpose: Accurate testing for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) is essential for breast cancer treatment. At present, immunohistochemistry (IHC)/florescence in situ hybridization (FISH) are widely accepted as the standard testing methods. To investigate the value of NanoString nCounter, we performed its comparative analysis with IHC/FISH and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) for the assessment of ER, PR, and HER2. Methods: Data on IHC/FISH results for ER, PR, and HER2 in 240 patients from a single tertiary hospital in Korea were collected and compared with NanoString nCounter and qRT-PCR results at a single institution. Results: Expression levels for each gene using NanoString nCounter showed good correlation with the corresponding data for protein expression by IHC (p<0.001) and gene amplification status for HER2 (p<0.001). Comparisons between gene expression and IHC data showed good overall agreement witha high area under the curve (AUC) for ESR1/ER (AUC=0.939), PgR/PR (AUC= 0.796), and HER2/HER2 (AUC = 0.989) (p<0.001). Conclusion: The quantification of ER, PgR, and HER2 mRNA expression with NanoString nCounter (R) may be a viable alternative to conventional IHC/FISH methods.