ErbB2 copy number variations in DNA in plasma from patients with esophageal carcinoma versus healthy controls and relative ROC curve analysis of the assay. (A) Box plot showing the ranges of erbB2 CN in DNA from the plasma of patients with EC (n.41) with respect to healthy controls (n.34). *P = 0.001. Horizontal bars in the box represent the medians of CN which is equal to 2 for patients and 1 for controls. (B) Receiver operating characteristic (ROC) curves (solid line; AUC, 0.95) were generated to compare healthy controls with EC patients for erbB2 with the null hypothesis (dashed line; AUC, 0.5; P = 1.39 × 10-11). The assay showed 80% sensibility and 95% specificity. Data are representative of three independent experiments.