GRP and lung cancer: In addition to radiographic evaluation, there have been numerous biomarkers to assist the diagnosis of lung cancer, such as carcinoembryonic antigen (CEA), cytokeratin 19 fragments (CYFRA 21-1), 2-phospho-d-glycerate hydrolase (NSE), squamous cell carcinoma antigen (SCC-Ag), and pro-gastrin-releasing peptide (Pro-GRP) (32, –, 34).