Implementation of a High-Accuracy Targeted Gene Expression Panel for Clinical Care

This study describes the validation of a clinical RNA expression panel with evaluation of concordance between gene copy gain by a next generation sequencing (NGS) assay and high gene expression by an RNA expression panel. The RNA Salah Targeted Expression Panel (RNA STEP) was designed with input from oncologists to include 204 genes with utility for clinical trial prescreening and therapy selection. RNA STEP was validated with the nanoString platform using remnant FFPE-derived RNA from 102 patients previously tested with a validated clinical NGS panel. The repeatability, reproducibility, and concordance of RNA STEP results with NGS results were evaluated. RNA STEP demonstrated high repeatability and reproducibility with excellent correlation (r > 0.97, p < 0.0001) for all comparisons. Comparison of RNA STEP high gene expression (log2 ratio ≥ 2) versus NGS DNA-based gene copy number gain (copies ≥ 5) for 38 mutually covered genes revealed an accuracy of 93.0% with a positive percentage agreement (PPA) of 69.4% and negative percentage agreement (NPA) of 93.8%. Moderate correlation was observed between platforms (r = 0.53, p < 0.0001). Concordance between high gene expression and gene copy number gain varied by specific gene and some genes had higher accuracy between assays. Clinical implementation of RNA STEP provides gene expression data complementary to NGS and offers a tool for prescreening patients for clinical trials.