Ca 72‐4 radioimmunoassay in the diagnosis of malignant effusions. Comparison of various tumor markers

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Abstract
We evaluated the utility of the CA 72‐4, CEA, CA 125, CA 19‐9 and CA 15‐3 radioimmunoassays for the detection of tumor‐associated antigens (TAAs) in effusions of malignant vs. benign origin. Fluids were obtained from 51 patients with adenocarcinomas, 27 with non‐epithelial malignancies, and 68 with benign disorders. The CA 72‐4 radioimmunoassay (cut‐off value 8.5 U/ml) detected the TAG‐72 antigen in 51% of adenocarcinoma patients′ effusions, while only 1 of 68 benign specimens had an elevated TAG‐72 level. Similarly, CEA levels above 5 ng/ml were found in 55% of the fluids from patients with adenocarcinoma and 3.2% of effusions from patients with benign disease. CA 19‐9 (cut‐off value 37 U/ml) exhibited a lower degree of sensitivity, with positive values in 23.5% of the effusions due to adenocarcinomas and in 4.5% of the effusions due to benign disease. At a cut‐off value of 29 U/ml, CA 15‐3 was positive in 49% of fluids from patients with adenocarcinoma and in 3.0% of the benign fluids. The CA 125 RIA failed to show any specificity using the established cut‐off value of 35 U/ml, with approximately 80% of all the effusions giving positive results. The specificity of the assay was increased by using a cut‐off value of 3000 U/ml, but with a substantial loss in sensitivity (23.5%). Using a combination of the CA 72‐4 and CEA RIAs the sensitivity for malignant effusions was increased to 73.5%. No additional improvement in the overall sensitivity was observed when using the CA 72‐4 assay in combination with assays for the other markers, except in the case of I effusion. We conclude that the CA 72‐4 RIA, possibly in combination with other assays such as CEA, may be useful in distinguishing between adenocarcinomatous and benign effusions.