Evaluation of the soluble fragments of cytokeratin 19 (CK19) in non-small cell lung cancer (NSCLC).

This study compared the diagnostic efficacy of serum CK19 determination (Cyfra 21-1) with other tumour markers, such as CEA, SCC, NSE, TPA, in patients with resected non-small lung cancer. Tumour marker levels were tested in 90 patients with benign lung disease and at diagnosis in 72 patients with proven NSCLC, 39 squamous cell carcinoma and 33 adenocarcinoma. At presentation baseline levels of all tumor markers were significantly higher (p<0.05) in lung cancer patients than in control subjects, except for NSE. A significant increase (p<0.05) in serum concentrations was observed from stage I to stage IIIb only for Cyfra 21-1 (stage I/II, median=2.7 ng/ml; stage IIIb, median=6.3 ng/ml) and TPA (stage I/II, median=89.8 IU/ml; stage IIIb, median=170.7 IU/ml). Receiver operating characteristic (ROC) analysis was performed to evaluate the best threshold values and the global accuracy of each marker. The highest global sensitivity for NSCLC was reached by TPA (70.8%), whereas that of Cyfra 21-1 was 50%. According to tumour histology, significant difference (p<0.05) in serum levels were found only for CEA (adenocarcinomas, median=5.6 ng/ml; squamous cell carcinoma, median=3.2 ng/ml) and SCC (adenocarcinomas, median=1.0 ng/ml; squamous cell carcinoma, median=1.5 ng/ml). As regards squamous cell carcinoma histotype, the highest sensitivity was obtained by TPA (74.4% at a specificity of 62.2%) and for adenocarcinomas by CEA (78.8% at a specificity of 85.6%). Tumour marker levels were also determined during the follow-up of 10 patients. The best sensitivity in detecting relapses was shown by CEA (90%), followed by TPA (70%), SCC (50%), Cyfra 21-1 (40%) and NSE (10%), even though the CEA test displayed a high percentage of false positive results (98.1%) in patients with no evidence of disease (NED).