Lung cancer is the most frequent and deadly malignancy worldwide and kills more people every year than colon, prostate, and breast cancer combined.Thus many efforts to improve diagnosis and therapy to increase the rate of lung cancer survival have been initiated during the last years.
Lung cancer is classified as non small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). SCLC accounts for approximately 20% of the new cases and differs clinically and biologically from the other histological types due to its neuroendocrine differentiation. The incidence of advanced disease at the time of primary diagnosis is high in SCLC. These tumors are, however, very sensitive to chemotherapy and radiotherapy.
Neuron specific enolase (NSE) has been the marker of choice in SCLC for prognosis, monitoring the course of disease and also for supporting diagnosis.However, NSE has relatively low sensitivity in early stage disease and is also influenced by hemolysis and other factors.
The difference in NSE levels between healthy subjects, benign disease and SCLC is also relatively small. These limitations of NSE has stimulated the search for better markers and efforts to find effective combionations of markersfor SCLC.
The neuropeptide hormone Gastrin Releasing Peptide (GRP) was described more than 25 years ago as a tissue marker of SCLC, but it was not possible to measure GRP in blood due to its very short half-life. GRP is synthesised as a prohormone, ProGRP, and this precursor of GRP is stable in serum. Immunoassays for ProGRP have been developed and the determination of ProGRP (peptide 31-98) has been shown to be a useful serum marker for SCLC.