Gastrin releasing peptide (GRP) was firstly isolated from porcine stomach in 1978 and then it was found to be present in many other organs and tissues, such as foetal lung and lung cancers, especially SCLC.5, 6, 7, 8 In 1988, the possibility of GRP being a biomarker of SCLC was aware.9 Since then, a quantity of studies explored GRP as a biomarker of SCLC but found it challenge because GRP is unstable and it is hard to measure its level in plasma. Here, GRP is linked to lung cancer.