Mucin-like cancer-associated antigen (MCA) compared with CA 15-3 in advanced breast cancer.

Mucin-like cancer-associated antigen (MCA), a new tumor marker using the mouse monoclonal antibody b-12 is thought to be of value in the management of patients with breast cancer. In this study sera from 191 female patients with breast cancer (112 with progressive disease [PD] and 79 with no evidence of disease [NED]) were analyzed for MCA levels and compared with those of cancer antigen 15-3 (CA 15-3) in single determination and in combination with carcinoembryonic antigen (CEA) and tissue polypeptide antigen (TPA). A cut-off level of 14 U/ml for MCA seems to be more appropriate than the recommended 11 U/ml to distinguish between PD and NED in patients with breast cancer. Although there was a fairly good correlation of MCA to CA 15-3, MCA was inferior in sensitivity and specificity to CA 15-3. Patients with osseous metastases and those with more than one metastatic site showed higher MCA levels than patients with visceral or soft tissue metastases, a fact which was comparable to CA 15-3. Combining MCA and CA 15-3 resulted in a gain in specificity but marked loss of sensitivity. The combination of MCA and CEA results also in a loss of sensitivity whereas the combination of CA 15-3 and CEA showed an increased specificity and only a negligible loss of sensitivity. The combination of MCA with TPA is of little value in the follow-up of breast cancer, as is the combination of CA 15-3 with TPA. The combination of CA 15-3 with CEA can be still recommended for follow-up for early detection of metastases in breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)