MEASUREMENT OF CYTOKERATIN 19 FRAGMENTS AS A MARKER OF LUNG-CANCER BYCYFRA-21-1 ENZYME-IMMUNOASSAY

Soluble cytokeratin fragment 19 levels were measured with an enzyme im munoassay method developed by Boehringer Mannheim (Enzymun-Test CYFRA 21-1) in the serum of 185 patients with lung cancer [149 with non-smal l-cell lung cancer (NSCLC) and 36 with small-cell lung cancer (SCLC)] and 97 patients with benign lung diseases in order to determine its cl inical usefulness in the diagnosis of lung cancer and follow-up of tre atment. We used the cut-off value of 3.5 ng ml(-1), established by the Japan CYFRA research group. This cut-off value is based on calculatio ns using the receiver operating characteristic approach instead of usi ng the 95% specificity approach recommended by other authors. The resu lting sensitivity and specificity for the group of all lung cancer pat ients were 65.4% and 84.5% respectively. The sensitivity was highest ( 76.1%) for squamous cell carcinoma and lowest (44.4%) for SCLC. For NS CLC patients, when CYFRA 21-1 levels were analysed by node (N) factor, patients who presented with mediastinal lymph node metastasis (N2 or N3) demonstrated higher serum CYFRA 21-1 levels (5.6; interquartile ra nge 3.2-11.5 ngml(-1)) than patients without mediastinal node metastas is (N0 or N1, 3.9; interquartile range 2.2-10.0 ng ml(-1); Mann-Whitne y U-test, P = 0.0373). We compared the discriminatory power of CYFRA 2 1-1 with that of other tumour markers including carcinoembryonic antig en (CEA), squamous cell carcinoma antigen (SCC) and neuron-specific en olase (NSE). The area under the curve (AUG) of each ROC curve was calc ulated using the CLABROC program for statistical analysis. CYFRA 21-1 appeared to have the most discriminatory power of the markers tested i n the diagnosis of lung cancer. In serial measurements of 14 patients receiving chemotherapy or radiotherapy, a high degree of correlation w as noted between serum levels of CYFRA 21-1 and extent of clinical res ponse (Wilcoxon, P = 0.0093).