If the PROGRP index is greater than about 100pg/ml, it suggests that the patient is very likely to have small cell lung cancer. PROGRP is also known as gastrin-releasing peptide precursor, which can represent the expression level of gastrin-releasing peptide. Because small cell lung cancer cells can secrete gastrin-releasing peptide, PROGRP is often used as a tumor marker for small cell lung cancer, and is also an important indicator used to distinguish small cell lung cancer from non-small cell lung cancer. Since the serum level of gastrin-releasing peptide precursor is related to the stage of small cell lung cancer, if the level is higher, then the condition is more serious. However, PROGRP alone cannot determine whether a patient is suffering from lung cancer or not, and needs to be combined with some other clinical symptoms, imaging examinations and pathologic examinations to make a diagnosis. Usually, small cell lung cancer is accompanied by chest pain, cough, coughing up blood, weight loss and other symptoms. If the patient is not feeling well or the examination is abnormal, it is recommended to go to regular hospitals for consultation, clear diagnosis and early treatment.