In the training set, there were 3/27 and 0/15 CEA‐positive, 6/27 and 6/15 NSE‐positive, and 2/27 and 0/15 CYFRA‐211‐positive patients, respectively, in the lung cancer and benign disease groups (P > 0.05 for all three biomarkers). This evidence concerns the gene CEACAM5 and lung cancer.