Pretreatment concentrations of breast carcinoma antigen (CA 15.3) and mucin-like carcinoma-associated antigen in patients with carcinoma of the breast.

Pretreatment serum concentrations of breast carcinoma antigen (CA 15.3) and mucin-like carcinoma-associated antigen (MCA) were determined in 129 patients with breast carcinoma. Concentrations of both markers were within the normal range in patients with Stage I disease. Concentrations of CA 15.3 were elevated (greater than 40 U/ml) in 3, 11 and 48%, those of MCA (greater than 17 U/ml) in 11, 18 and 52%, and those of one or the other marker in 11, 18 and 58% of the patients with Stage II, III and IV disease, respectively. The elevation of either marker roughly paralleled the size of the tumor being normal in the patients with localized cancer, slightly elevated in a small proportion of the patients with locoregional cancer, and moderately to markedly elevated in half of the patients with distant metastases. Correlation between serum concentrations of CA 15.3 and MCA was highly significant (p less than 0.0001). It is concluded that the markers were equally sensitive and that an elevated serum level was a useful adjunct for staging, implying systemic disease.