To elevate the diagnostic value of the serum cytokeratin 19 fragment (
CYFRA 21-1) and compare it with carcinoembryonic antigen (CEA) and tis
sue polypeptide antigen (TPA) in bronchogenic carcinoma, the sera of 1
61 patients (58 with benign pulmonary disease and 103 with bronchogeni
c carcinoma) was investigated using immunoradiometric assay. Sensitivi
ties for CYFRA 21-1, CEA and TPA (using 3.5 ng ml(-1), 5.0 ng ml(-1),
110 Ul(-1), respectively, cut-off values corresponding to a 95% specif
icity for benign pulmonary disease) in bronchogenic carcinoma were 64,
47 and 61%, respectively. Positive CYFRA 21-1 levels were identified
in 75% of patients with squamous cell carcinoma (n=36), in 67% with ad
enocarcinoma (n=45), iq 17% with large cell carcinoma (n=6), and in 50
% with small cell lung cancer (SCLC) (n=16). However, CYFRA 21-1 level
s were not significantly different between squamous cell carcinoma and
the other histological types. The sensitivity of the combined measure
ment of CYFRA 21-1 with any other tumour marker was significantly high
er than that of CYFRA 21-1 measurement alone. Elevated CYFRA 21-1 leve
ls were observed in 44% of Stages I and II (n=18) and 72% of Stages II
I and IV (n=69) patients with non-small cell lung cancer (P<0.05). A s
ignificant inter-marker correlation was observed between CYFRA 21-1 an
d TPA (n=103, r=0.448, P<0.0001). Twenty-one patients were monitored b
y CYFRA 21-1, and significantly different changes in progressive patie
nts (P=0.0058) and regressive patients (P=0.016) were obtained. These
results indicate that CYFRA 21-1 may be not only a sensitive tumour ma
rker in the diagnosis of bronchogenic carcinoma, but also a useful mar
ker for the monitoring of bronchogenic carcinoma.