Usefulness of Serum Tumor Markers, Including Progastrin-Releasing Peptide, in Patients with Lung Cancer: Correlation with Histology

Background: Tumor markers have been extensively studied in lung cancer, reporting some relationship to the histology, but their clinical utility is not clear. Methods: ProGRP, CEA, SCC, CA 125, CYFRA 21-1 and NSE were studied prospectively in 155 patients with unconfirmed suspicion of lung cancer and in 647 patients with lung cancer: 182 squamous, 205 adenocarcinomas, 19 large-cell lung cancer (LCLC), 175 small-cell lung cancer (SCLC) and 66 unspecific non-small-cell lung cancer (NSCLC). Results: Abnormal tumor marker serum levels were found in less than 5.3% of the patients with benign diseases, excluding CA 125 (21.3%). Tumor markers were related to histological type and tumor extension with significantly higher CEA (p <0.01) and CA 125 (p <0.007) serum levels in adenocarcinomas, SCC (p <0.0001) and CYFRA 21-1 (p <0.008) in squamous tumors and ProGRP (p <0.0001) and NSE (p <0.0001) in SCLC. Tumor markers may be useful in the histological differentiation of NSCLC and SCLC. Patients with SCC serum levels >2 ng/ml were always NSCLC, while those with SCC <2 ng/ml and ProGRP >100 pg/ml and NSE >35 ng/ml were all SCLC patients. The sensitivity was 76.7 and 79.5%, specificity was 97.2 and 99.6%, with a positive predictive value of 98.6 and 98.6% and a negative predictive value of 60.7 and 92.9% in the differentiation of NSCLC and SCLC, respectively. Conclusions: Tumor marker determination in patients with suspicious signs of lung cancer suggests, in a few hours, the histological diagnosis in the majority of lung cancer patients.