7P Independent validation of HER2DX ERBB2 mRNA score to predict HER2-positive (HER2+), HER2-low and HER2-0 status in breast cancer

HER2DX ERBB2 mRNA score captures the dynamic range of expression in both HER2-negative and HER2+ breast cancer (BC). In a previous study (Prat et al. EBiomedicine 2022), predicted clinical status with high performance validation dataset (n=353; AUC=0.96). Here, we evaluated ability to predict HER2+, HER2-low, HER2-0 status. Standardized was centrally on formalin-fixed paraffin-embedded tumors from 1,149 samples (n=1,029) vs. (n=120). We trained new cutoff (by means decision trees) HER2-low (n=73) versus (n=47) status, tested an independent 110 known (n=60) (n=50) To quantify diagnostic performance: area under ROC curve (ROC AUC), global accuracy, positive (PPV) negative predictive value (NPV) were calculated. (n=1,149), AUC 0.98. The mean (in log base 2) disease 1.41 -2.41, respectively (14.1-fold difference). Of note, 0.8% cases identified as ERBB2-positive 9.9% negative. training (n=120), 0.80, 77.5% accuracy (68.5% PPV 84.9% NPV). (n=110), 0.77. With cutoff, overall 65.5% (66.7% 64.9% Finally, -1.86 -2.72, (1.8-fold standardized predicts HER2 (positive, low zero) BC.