Clinical utility and validation of emerging biochemical markers for mammary adenocarcinoma.

The clinical utilities of the emerging biochemical markers for mammary adenocarcinoma CA 15-3, CA 549, CA M26, CA M29, and MCA (mucin-like carcinoma-associated antigen) were assessed by a formal rating according to six desirable marker characteristics. All five indicators similarly have good specificities but limited sensitivities. As a consequence, these markers mainly meet just two desirable criteria: their frequency and degree of expression reflect tumor burden and prognosis, and they may correlate with therapeutic results. The validation of these assay properties by clinical trials was evaluated by another rating system, designed to assess proband sample selection, restrictions on allowable observations, and choice of statistical descriptors. By these benchmarks, the estimates of the prior probabilities of test outcome (sensitivity and specificity) are reasonably definitive, but conclusive judgments about the posterior probabilities of test outcome ("predictive values") and about values and costs associated with testing are not possible. Three approaches to enhance the limited clinical utility of biochemical breast cancer markers are considered: shifts of the diagnostic decision threshold, marker panels, and sequential testing. However, none of these strategies improves the described performance characteristics.