We then performed receiver operating characteristic (ROC) curve analyses for each of these genes (Fig. 4): five genes (GSTP1, RARB, RASSF1, SCGB3A1 and CCND2) were highly specific in discriminating between prostate cancer and adjacent normal tissue, with an area under ROC curve (AUC) ranging from 0.89 (95 % CI 0.82–0.97) to 0.95 (95 % CI 0.90–1.00). The gene discussed is RARB; the disease is prostate carcinoma.