To Screen or Not to Screen

In the latest issue of the Journal of the American Medical Association is an article questioning the value of breast cancer screening. In it, Professor Laura Esserman of the University of California, San Francisco, analyzes the incidence of early versus advanced breast cancers in an era prior to screening and then sixteen years later, when screening became established. While mammography did increase the rate of early breast cancer detection, there was no change in the rate of advanced disease, which one would have expected. What to make of this data?

One interpretation is likely to generate much more discussion than we in the oncology community have engaged in: that some cancers are actually not lethal, and hence, do not require treatment. The data from Esserman and colleagues point to the increased pick up of these “benign” cancers and the potential that they have been over-treated. In an era of MRI, this has become an entirely more relevant issue as MRI’s increased sensitivity to detect smaller breast lesions often leads to changes in surgical treatment, from conservation to mastectomy—without knowing what impact it has on overall survival.

So, does this mean we should not screen? In an earlier post I highlighted an analysis that Cady and colleagues performed demonstrating that mortality from breast cancer was higher in those not undergoing mammographic screening. How can we reconcile these data sets?

These studies point to how much we have yet to learn about breast cancer. In truth, oncologists are not yet able to discriminate those cancers with malignant potential from those not threatening. Hence, we resect all invasive tumors found, because of the “potential” to be fatal. Certainly, there is reason to be concerned for over-treatment, both medical and surgical, but faced with a risk that left on its own a tumor could kill you, the choice seems obvious- treat it.

Mammography saves lives—that is the take home message from Dr. Cady’s analysis. However, it will not save every woman’s life- particularly those with rapidly progressive lesions which often present as advanced disease. This is the message of the Esserman study.

So, what’s my take on this: I would not recommend against screening. To do so would likely undo much of what we already have learned about early detection in breast cancer.