VALUE OF CA-15.3 IN BREAST-CANCER AND COMPARISON WITH CEA AND TPA - ASTUDY OF SPECIFICITY IN DISEASE-FREE FOLLOW-UP PATIENTS AND SENSITIVITY IN PATIENTS AT DIAGNOSIS OF THE FIRST METASTASIS

The specificity and sensitivity of a tumor marker (TM) are important i n establishing its potential clinical utility for a specific type of n eoplasm. CA 15.3 is a TM specific for breast cancer; it is defined by two monoclonal antibodies (DF3 and 115D8), whose specificity, in disea se-free follow-up patients, and sensitivity, in patients at diagnosis of first metastasis, have been evaluated in the present study and comp ared with those of carcinoembryonic antigen (CEA) and tissue polypepti de antigen (TPA). Serum concentrations of all three TMs were quantifie d in 618 individuals: 80 healthy controls, 421 patients with local bre ast cancer who became free of disease following locoregional treatment , and 117 patients with disseminated disease at diagnosis of metastasi s. Radioimmunoassay (RIA) was the method employed, and the cut-off val ues obtained were 30 U/ml for CA 15.3, 5 ng/ml for CEA, and 120 U/I fo r TPA. The results showed CA 15.3 and CEA specificities to be analogou s (95.7 and 95.5%, respectively). TPA specificity (81.9%) was lower(p< 0.001). During adjuvant therapy, CA 15.3 serum levels were seen to inc rease, followed by a normalization of concentration after terminating therapy. On the other hand, CA 15.3 and TPA sensitivities (64.1 and 67 .5%, respectively) were greater than for CEA (44.4%, p<0.01). It is co ncluded that CA 15.3 is a useful TM for breast cancer, as it offers a greater sensitivity than CEA and a higher specificity than TPA. Combin ing CA 15.3 and CEA fails to increase CA 15.3 sensitivity, while combi ning CA 15.3 with TPA increases false-positives and so likewise offers no additional benefit.