Background: It is known that cytokeratin 19 is particularly abundant in carcinoma of the lung.
Methods: A sandwich enzyme-linked immunosorbent assay called CYFRA 21-1 was, therefore, developed to detect soluble cytokeratin 19 fragments in serum using two specific monoclonal antibodies (Ks 19.1 and BM 19.21). The authors investigated the clinical significance of this new marker compared with the established markers carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC), neuron-specific enolase (NSE), carbohydrate antigen (CA) 19-9, CA 125, CA 15-3, CA 72-4, alpha-fetoprotein, and prostate-specific antigen in a pilot study on 1741 serum samples from patients with various benign and malignant diseases.
Results: Postulating a specificity of 95% versus benign diseases of the lung, the diagnostic sensitivity of CYFRA 21-1 in lung cancer (independent of histologic type) at primary diagnosis was superior (47%) to CEA (27%), SCC (15%), and NSE (16%). Especially in squamous cell carcinomas of the lung, the true-positive test results were much higher for CYFRA 21-1 (60%) than for CEA (18%) or SCC (31%).
Conclusions: In small cell lung carcinomas, NSE was confirmed as the marker of first choice. For all of the other solid tumors investigated, CYFRA 21-1 showed no better profile of specificity and sensitivity than the established markers.