Plasma proGRP Concentration is Sensitive and Specific for Discriminating Small Cell Lung Cancer from Nonmalignant Conditions or Non-small Cell Lung Cancer

To date, most clinical data on pro-gastrin-releasing peptide (proGRP) have been based on serum concentrations. This study evaluated the agreement between proGRP levels in fresh serum and plasma in patients with various lung diseases. Pairs of serum and EDTA plasma were collected from 49 healthy individuals. At the same time, EDTA plasma of 118 lung cancer patients and 23 patients with benign pulmonary diseases were prospectively collected. Compared to serum, plasma proGRP concentrations were higher by an average of 103.3%. Plasma proGRP was higher in malignancy (336.4 ± 925.4 pg/mL) than in benign conditions (40.1 ± 11.5 pg/mL). Small cell lung cancer (SCLC) patients showed higher levels of proGRP (1,256.3 ± 1,605.6 pg/mL) compared to other types of lung cancer. Based on the ROC curve analyses at a specificity of 95%, the diagnostic sensitivity of plasma proGRP was estimated to be 83.8% in distinguishing SCLC from all the other conditions, and 86.5% for discriminating SCLC from the nonmalignant cases. Among the SCLC cases, limited stage disease had lower levels of plasma proGRP than extensive disease. When measuring circulating levels of proGRP, the use of plasma is preferred over serum. Plasma proGRP has a potential marker for discriminating SCLC from nonmalignant conditions or non-small cell lung cancer.