Background. In spite of many advances in the analytical reagents (anti
bodies), analytical systems, and the clinical application of tumor mar
kers, the present markers do not detect early stage cancer. Preliminar
y data with an antigen specific to tumor tissue, cancer procoagulant (
CP), suggest its possible role in the detection of early stage cancer.
This study was aimed at determining the clinical use of CP as an earl
y stage tumor marker. Methods. An improved enzyme-linked immunosorbent
assay (ELISA) was developed to measure CP concentration in serum. A p
anel of 817 blinded serum samples were examined from three groups of p
eople: 573 cancer, 106 benign, and 139 normal.Results. The sensitivity
of all samples analyzed from cancer patients was 80%. The CP ELISA wa
s able to detect ovarian, colon, and kidney cancer at a sensitivity gr
eater than 85%; breast, prostate and small cell lung cancer was detect
ed at a sensitivity of 80-85%. Particularly interesting was the observ
ation that early stage cancers, regardless of site, were detected effe
ctively. In some groups, the CP assay correctly identified 100% of the
patients with stage I and II cancer. The assay was able to identify c
orrectly noncancer patient sera at a specificity of 83% for those with
benign disease and 82% for the normal individuals. Conclusions. The C
P assay has potential as an aid in diagnosing early stage malignancies
and thereby may significantly improve the survival rate of cancer pat
ients.