RESUMEN
PURPOSE: Cancer antigen 153 (CA 15-3) is one of the most commonly used biomarkers of breast cancer. However, elevated CA 15-3 is reported in pregnant and lactating women more frequently on Beckman DxI 800 immunoassay system (Ma695-Ma552 antibody pair) than on Abbott ARCHITECT system (115D8-DF3 antibody pair) in laboratory methodological evaluation. We conducted this study in order to figure out the reason behind this phenomenon. METHODS: Serum CA 15-3 concentration was analyzed in 426 subjects, including 180 patients with breast cancer, 121 patients with benign breast disease, and 125 healthy volunteers (45 pregnant and 80 non-pregnant women). CA 15-3 assay was further validated using another cohort of 112 pregnant or postpartum women. Immunological cross reaction was analyzed by Western blotting and immunoprecipitation. RESULTS: The serum CA 15-3 level was abnormally higher in almost 95% of the pregnant and lactating women detected using Ma695-Ma552 antibody pair (median: 71.4 U/mL) than that detected using 115D8-DF3 antibody pair (median: 16.5 U/mL). Western blotting and immunoprecipitation indicated that such a significant difference was mainly due to the cross reaction between monoclonal antibody Ma552 and mucin-like carcinoma-associated antigen (MCA). CONCLUSIONS: The CA 15-3 assay using 115D8-DF3 antibody pair is more suitable for monitoring therapy in pregnancy-associated breast cancer.