Comparison of mammary serum antigen assay with mammography in patients with breast cancer.

Mammary serum antigen levels and two-view xeromammography were evaluated in a study of 97 patients who presented at a specialist breast clinic in a major teaching hospital, in order to determine their single and combined value in the detection of breast cancer. Raised mammary serum antigen levels (greater than 300 inhibition units) were found in 76% of patients with stage-1 (including carcinoma-in-situ) and stage-II breast cancer compared with 54% of patients whose mammograms were suggestive of cancer (probability of carcinoma, greater than 50%). Four patients with carcinoma-in-situ had elevated mammary serum antigen levels, but their mammograms did not suggest the presence of cancer (probability of carcinoma, less than 50%). The over-all sensitivity, specificity and predictive value of a positive test-result in detecting breast cancer were 76%, 82% and 72%, respectively, for the mammary serum antigen test, and 54%, 88% and 74%, respectively, for mammography. When the mammary serum antigen test and mammography were used together, a combined evaluation enhanced the sensitivity in the detection of breast cancer (89%) but with a concomitant reduction in specificity (72%). The mammary serum antigen test was superior to mammography in the detection of breast cancer in this study and may prove to be a useful adjunct to conventional methods of clinical assessment and to mammography for the detection of breast cancer.