COMPARATIVE-EVALUATION OF SERUM CA-195 AND CARCINOEMBRYONIC ANTIGEN IN METASTATIC CARCINOMA

Background. Carcinoembryonic antigen (CEA) is a well-described human t umor-associated antigen most useful clinically in colon cancer. Howeve r, the clinical usefulness of CEA is limited by the marker's overall p oor specificity and low sensitivity in patients with minimal disease. CA 195 is a recently discovered human tumor-associated glycoprotein th at can be measured in serum using an immunoradiometric assay. CA 195 i s expressed on the membrane of human colon cancer cells and shares an epitope with the Lewis A blood group antigens. The authors initiated a study to compare the clinical utility of serum CA 195 with CEA in pat ients with advanced cancer. A control population was studied to assess the effects of age, gender, alcohol, and tobacco on the measured leve ls of serum CA 195. Methods. Using a solid-phase two-site immunoradiom etric assay, serum CA 195 and CEA levels were measured in 71 control s ubjects and 167 patients with a prior diagnosis of cancer. The tumor h istologic types included breast cancer, 49 patients; colon cancer, 38; prostate cancer, 24; lung cancer, 22; gastrointestinal noncolon cance r, 7; and miscellaneous, 27. Among patients with a history of cancer, 124 (74%) had active metastatic disease, and 43 (26%) were without evi dence of active disease. The control population was composed of subjec ts without a history of malignancy. Clinical data collected from them included age, gender, smoking history, and alcohol consumption. Result s. In this laboratory, the normal ranges established for CA 195 and CE A in the control group were: 0.0-8.3 U/ml and 0.2-4.2 ng/ml, respectiv ely. In the control subjects, the serum CA 195 level, unlike that of C EA, was not affected by age, gender, alcohol consumption, or tobacco u se. In the study population, CA 195 had either equivalent or inferior specificity and sensitivity to CEA in all tumor types. A determination of the additive specificity and sensitivity of CA 195 and CEA did not significantly improve its clinical utility compared with CEA alone. H owever, CA 195 was significantly elevated in three patients with a pri or history of colon cancer thought to be without evidence of active di sease. Because all three of these patients had a relapse within the ne xt 1-15 months, CA 195 might identify early relapses of colon cancer i n some patients. Conclusions. Based on these results, it was concluded that CA 195 is not superior to CEA as an indicator of disease activit y in advanced colon cancer or other solid tumors. However, studies uti lizing CA 195 in the detection of early relapses of colon cancer may b e warranted. A review of the English literature revealed that CA 195 m ight be a useful marker in pancreatic cancer.