Comparison of mammary serum antigen (MSA) with β 2-microglobulin (β 2M) and carcinoembryonic antigen (CEA) assays in patients with breast cancer

Abstract

Serum levels of mammary serum antigen (MSA), β 2-microglobulin (β 2M) and carcinoembryonic antigen (CEA) were evaluated in 186 subjects to assess their use in the diagnosis and monitoring of breast cancer, either singly or in combination. Raised MSA levels (>300 I.U.) were detected in 79% of patients with Stage I/II breast cancer, compared with 25% for β 2M (>2000 μ g/l) and 12% for CEA (>5 ng/ml) levels respectively. Of 53 patients with Stage III/IV breast cancer, 98% (MSA), 55% (β 2M) and 64% (CEA) had raised levels. In 25 patients followed over 3–9 months, the changes in MSA levels correlated with the clinical course of the disease in 23 25 (92%), compared with 7 25 (28%) using β 2M, and 9 25 (36%) using CEA assays. The overall sensitivity, specificity and accuracy in detecting breast cancer were 88%, 95% and 99% for MSA; 39%, 90% and 96% for β 2M; and 38%, 95% and 98% for CEA, respectively. MSA and β 2M assays in combination enhanced the sensitivity in the detection of breast cancer (93%) especially early breast cancer, while maintaining specificity (90%). MSA seems to be superior to β 2M or CEA as a tumour marker in breast cancer and its levels seem to correlate with tumour burden. While it appears that β 2M or CEA measurements used alone are of little value in the current management of breast cancer, β 2M may be a helpful adjunct to enhance the sensitivity of MSA assay especially in early breast cancer.