New markers for breast carcinoma-associated antigen in comparison with CA 15-3

The objective of this study was the clinical comparison of newly developed antibodies used in commercially available test systems with CA 15-3 (CIS bio international). IMMULITE BR-MA is a sequential chemoluminescent assay using the Mab's Ma552 and Ma695. Truquant BR RIA is a competitive inhibition radioimmunoassay using the Mab B27.29. ELSA-CA 15-3 is a sequential immunoradiometric assay using the Mab's115D8 and DF3. In the study 32 breast cancer patients (206 serum samples) were included during therapy monitoring. Linear regression analysis was performed with the CA 15-3 test as the reference method. Clinical criteria of response were according to UICC). Regression analysis in the range 0-1000 kU/l revealed the equations: IMMULITE = 1.65CIS + 0.87 (r = 0.78) and Truquant = 1.16 CIS + 10.6 (r = 0.95). The upper reference level of normal controls were somewhat higher than using the CIS method (30 kU/l): IMMULITE and TRUQUANT 40 kU/l and 36 kU/l, respectively. In all patients (except in 1 serum sample) nearly complete parallel tumour marker changes were seen with only minimal discrepancies in a few patients. However, the average factor between different patients varied between 0.51-6.9 (IMMULITE) and 0.74-2.3 (Truquant). In comparison to UICC criteria no discrepancies were observed. Therefore, we concluded that the test systems from DPC and BIOMIRA for the CA 15-3 antigen can replace the CIS test. Patient results were not interchangable. All test systems followed the clinical course of the disease in the same way.