The article "Breast cancer screening risks not swaying women" (Sept. 24) on the "risks" of breast cancer screening is timely.

The article is about research indicating women are unaware of the risks of screening mammography. This is hotly debated in medical literature right now, with some researchers speculating that screening may be unethical because of these "risks."

What are the risks? The U.S. Preventive Services Task Force (USPSTF) noted the risk of the anxiety related to being called back for additional mammography scans after screening, when it turns out a woman called back doesn't have cancer. They termed this a "harm." Being called back for additional views from screening happens at most once in 10 years on average for women 40 to 49, and less for older groups, according to the USPSTF author's own publication.

Also, the USPSTF cites the "harm" of being subjected to a biopsy when the biopsy doesn't show cancer. This is, on average, a once in a 100-year "harm" for the youngest group, and much less often for older groups.

In addition, the USPSTF notes the radiation exposure from a mammogram — comparable to that received during a long flight from cosmic radiation. Is this a significant "harm"?

The USPSTF made a screening mammography recommendation of every other year for ages 50 to 74 based on models estimated to save approximately 23 percent of women from breast cancer. The American College of Radiology recommends yearly screening from ages 40 to 84, saving an estimated 39 percent of lives. Admittedly, this is at a cost of several times more mammograms, which is my conflict of interest. But a lot more women die from the USPSTF schedule. And current law mandates that insurers cover screening annually for those 40 and older at no charge to the woman. (Callbacks and biopsies are subject to deductibles and copays, however, which can be substantial.)

Of course, the real problem isn't the "harms" of screening, or even the favorite whipping child of screening detractors: overdiagnosis. The overdiagnosis is a "harm" if it leads to overtreatment. Overtreatment can be associated with "harms" that are much more real to me than screening callbacks or biopsies that turn out to be negative. Even when therapies for breast cancer are uncomplicated, the scars from surgery and radiation are not trivial. And the chance of a swollen arm from surgery or X-ray therapy to the armpit, the loss of mental function, hair loss, mouth sores, etc., from chemotherapy, and the premature aging effect of tamoxifen are not to be taken lightly. Of course, only the ravages of the natural course of breast cancer can justify the side effects from treatment. And so it is extremely important that we continue to determine the least therapy necessary for adequately treating a given cancer.

By the way, measurements of "overdiagnosis" by screening mammography are imprecise. This is because the number of breast cancers diagnosed in the United States had been increasing every decade since the 1940s before screening mammography started. When researchers assume that for some reason the number of breast cancers stopped increasing when we started screening mammography, as many authors do, then overdiagnosis related to screening mammography appears much higher than if they assume that the number of breast cancers continued to increase at the same rate after we started screening.

Finally, if overtreatment occurs, current research focuses on the earliest cases of cancer, called low grade DCIS. Three studies in the U.S. and the U.K. are examining this hypothesis of overtreatment. Patients who fit criteria aren't being operated on in the study group to see what happens. As a radiologist, I applaud efforts of my surgery, medicine and radiation therapy colleagues to determine which therapy is most appropriate so that patients are neither over- nor undertreated, and we continue to reduce breast cancer deaths as has been happening since screening mammography was initiated in the 1980s.

Tim Emory is a radiologist and director of breast imaging at the University of Minnesota Medical School.