[Debbie L.]

I've been meaning to weigh in on this interesting discussion for awhile.

AA asks: "Wouldn't it make better practical sense to routinely administer at least a CA 15-3 or a CA 25.29 (even though not wholly reliable)") . . .

My answer to you, AA, would be that those two markers are even less than "not wholly reliable" when used as a screening tool.

Here's what a 2007 medline reference says:
"Currently, insufficient data exists to recommend the use of CA 15-3 measurement for screening, diagnosing, or staging breast cancer.[6] CA 15-3 levels are elevated infrequently in early-stage breast cancer or completely absent from other breast cancers, making it difficult to detect early-stage cancers or those tumors that do not express this antigen. However, several studies report prognostic value of the CA 15-3 marker in early-stage breast cancer.[6, 7] Presence of this tumor marker may predict a worse outcome, but the implication on management of early-stage breast cancer remains unclear. This marker has no clinical value in breast cancers that do not produce the CA 15-3 marker.
CA 15-3 levels may also be increased in several benign and malignant conditions. This results in low sensitivity, specificity, and positive predictive values, making it difficult to reliably screen, diagnose, or stage breast cancers. The CA 27.29 assay is slightly more sensitive for breast cancer, but its indications and limitations are identical to the CA 15-3 assay.[6]"

In discussion of the same issue, breastcancer.org says only 30% of those with primary breast cancer will have elevated CA 15-3 levels.

Plus, false positives are common and can be caused by other conditions than cancer, or by cancers of non-breast origin.

I think there is a fair amount of research interest right now in a better marker (or markers, like in the article Lani posted) for screening for breast cancer.

I don't want to be a total wet blanket here, but several things about this concern me. First of all, we still don't really know how early is early enough, for the most aggressive cancers. There may be a segment of cancers that metastasize nearly immediately, making those breast cancers a systemic disease long before they are detectable. The inability of all this research to show a strong benefit to mammography is supporting evidence for this idea.

My second concern is that if we detect a breast cancer TOO soon with a blood test, we don't know what to do about it. We don't know how big a threat it is or has the potential to be. We don't know if it has to be surgically removed or if some kind of systemic treatment could nip it in the bud. What if (and this would happen frequently) a blood test indicated breast cancer, but no lump could be found? Would we begin lopping off both breasts of all women who receive a positive result?

I wish we had better answers -- I wish we had a reliable method of very early detection and the knowledge of what to do with that information, to save lives. But we don't have that information. At this point, it is possible that all we'd do with earlier detection is cause a whole lot of anxiety, spend a whole lot of money, and cause suffering (treatment) -- all with no lives saved in the end. I think we need to think carefully before we get too far down this road.

I've come to believe that the answer doesn't lie in this direction. I agree with NBCC that the answer lies in prevention of primary disease and prevention of metastasis.

Debbie Laxague