Serum (circulating) tumor markers for breast cancer.

Many circulating markers have been proposed for breast cancer, with potential utility for identification, screening, prognosis, detection, or monitoring. Of the available markers, those with the greatest promise include circulating tumor markers that provide an indication of clinical course, such as CA15-3 and CEA, and novel markers such as BrCa1, antibodies to p53, antibodies to HER-2/neu, indicators of angiogenesis, and the extracellular domain of HER-2/neu. However, the precise clinical utilities of all of these markers have yet to be determined. It is especially important that the relative independence of the markers in relation to other available markers be determined so as to avoid the unnecessary cost and expense of redundancy. Moreover, it is important that the clinician be aware of the limitations in both sensitivity and specificity of each marker so as not to over- or under-interpret the predictive value of any test.