Computer-Assisted Detection and Screening Mammography: Where’s the Beef?

Extract

Screening for cancer presents inferential issues that are among the most difficult in science. Whether screening should be recommended and for whom is seldom clear, despite extensive experience in randomized trials, in observational studies, and in ordinary practice. “Finding early” is the easy part. Cancers found early by screening and by improvements in screening technology may or may not be worth the finding.

In general, improvements in screening mammography lead to finding more cancers and/or decreasing the number of false-positive results by improving sensitivity or specificity, respectively. A more important consideration is whether the finding improves the patient’s lot, that is, is identifying a particular cancer and treating it earlier doing the woman a favor? Perhaps, the cancer was not lethal, and without the new technology, it would not have been found for many years. A woman having such a cancer could have spent these years “cancer free” with no decrement in survival. Indeed, the cancer might never have been found otherwise, resulting in overdiagnosis. We know that the incremental cancers found by mammography are biologically different from symptomatic cancers and not just because of a stage shift ( 1–5 ). The problem is that we do not yet understand the biology of cancer well enough to know which cancers are important to find early and which can be ignored.