GRP and lung cancer: Lung cancer related serum tumor markers were negative, including carcinoembryonic antigen (CEA, 1.72 ng/ml, 0-5.0ng/ml), pro-gastrin-releasing peptide (Pro GRP, 27.90 pg/ml, <69.2pg/ml), recombinant cytokeratin fragment antigen 21-1 (CYFRA21-1, 1.87ng/ml, <3.3ng/ml), carbohydrate antigen 125 (CA125, 14.1 U/ml, <35.0 U/ml), neuron-specific enolase (NSE, 15.24 ng/ml, <16.3 ng/ml), and squamous cell carcinoma antigen (SCC, 1.28 ng/ml, <2.7 ng/ml).