Carcinoembryonic antigen, neuron-specific enolase and cytokeratin fragment 19 (CYFRA 21-1) levels in induced sputum of lung cancer patients

Objectives. The diagnosis of lung cancer is usually based on the histological and cytological examination of material obtained by bronchoscopy. Tumour markers in serum are of little use as a diagnostic tool for lung cancer. We hypothesized that induced sputum could be a suitable material for measuring tumour markers and, accordingly, attempted to evaluate the diagnostic value of such measurements in lung cancer. Induced sputum is minimally invasive and readily obtainable. Material and methods. Fifty patients with lung cancer and 24 subjects with chronic obstructive pulmonary disease (COPD) were included in the study. CEA, NSE and CYFRA 21-1 levels in serum and induced sputum were measured by immunoradiometric assays. Results. Serum and sputum CEA, serum and sputum NSE and serum CYFRA 21-1 did not differ significantly between lung cancer and COPD patients. Sputum CYFRA 21-1 was 7 times greater in the lung cancer group than in the COPD group. This finding was true in both small cell (SCLC) and non-small cell (NSCLC) lung cancer. The sensitivity, specificity, positive and negative predictive values were 86, 75, 88 and 72 %, respectively. Conclusion. Of tumour markers in induced sputum, sputum CYFRA 21-1 offered the best predictive values, although not sufficiently satisfactory to suggest its routine use in lung cancer diagnosis.