Serum CA549 in primary breast cancer: comparison with CA15.3 and MCA.

We carried out a comparison of three commonly used mucin markers, CA549, CA15.3 and MCA. Serum samples from 184 healthy women and 237 patients with primary breast cancer were evaluated. The markers were measured using commercially available immunometric assays. Like CA15.3 and MCA, CA549 was significantly associated with tumour size and lymph node status, being an effective indicator of tumour bulk. CA549 was significantly correlated with both CA15.3 and MCA. Positive/negative concordance rate was very good (93.7%) between CA549 and MCA. Conversely, CA15.3 was positive and CA549 negative in 20.4% of cases. Axillary status was not significantly different in the latter group of patients and in cases in which CA15.3 and CA549 showed concordant results. From the present findings we draw the following major conclusions: 1. CA549 and MCA are highly correlated and their association should not provide additional information; however, they should not be considered interchangeable since they may behave differently in individual cases. 2. CA549 and CA15.3, although well correlated, are discordant in a significant number of cases. Longitudinal studies are needed to verify the usefulness of the association between the two markers. 3. The three evaluated mucin markers are not interchangeable in individual patients; if a patient is monitored with a marker, she should be followed up with the same marker.