Preliminary evaluation of the new tumor marker, CYFRA 21-1, in lung cancer patients.

Serum samples from 137 lung cancer patients were examined by RIA to evaluate the clinical efficacy of the new tumor marker, CYFRA 21-1, which could identify the soluble fragment of cytokeratin 19. The cut-off value was determined to be 2.2 ng/ml according to the receiver operating characteristic curve. The sensitivity, specificity and accuracy of the RIA for CYFRA 21-1 were 57.7, 91.9 and 64.9%, respectively. The serum concentration of CYFRA 21-1 and the sensitivity of the assay increased as the disease progressed. Histologically, the sensitivity was highest for squamous cell carcinomas (SQ) (76.5%) in comparison with adenocarcinomas (47.8%) and small cell lung cancers (42.1%) (P < 0.01, P < 0.05, respectively). The sensitivities for SQ were 60.0, 83.3, 80.0 and 100% at stages I, II, III and IV, respectively. When compared with CEA (45.3%) and squamous cell carcinoma related antigen (SCC) (22.6%) in all lung carcinomas, CYFRA 21-1 showed the highest sensitivity (57.7%), (P < 0.05, P < 0.01, respectively). In SQ, the sensitivity of the CYFRA 21-1 RIA was significantly higher than that of the assay for SCC (47.1%) (P < 0.05). In patients with adenocarcinomas, the sensitivity of the CYFRA 21-1 assay was almost the same as that for CEA (49.3%). In a combination of CYFRA 21-1 and CEA for non-small cell lung cancers (NSCLC), the sensitivity and accuracy increased to 75.4 and 78.1%, respectively, although the specificity decreased to 86.5%. It is concluded that CYFRA 21-1 could replace SCC, a less satisfactory tumor marker, for SQ of the lung. The potentiality of the combination of CYFRA 21-1 and CEA for NSCLC should be estimated using larger samples in the near future.