What to Make of the Mammography Controversy

The recent change in mammogram recommendations by the U.S. Preventive Services Task Force is long overdue, and the controversy surrounding it highlights an important problem in healthcare in the U.S. Namely that we are terrible at setting priorities.

Without summarizing all of the details, the task force has interpreted the available data and now recommends that mammograms for women at normal risk for breast cancer start at age 50 rather than 40 and be done every two years rather than every year. The U.S. was way behind on this, most countries in the world avoided the mistake of exposing average-risk women under age 50 to unnecessary radiation a long time ago. In addition, the task force has recommended we stop teaching women to do self breast exams (a time-honored practice that has led to a lot of worry and anxiety in women but has never been shown to save lives.)

The reaction to this recommendation has been loud and predictable. The American Cancer Society, numerous breast cancer advocacy groups, politicians, and doctors who get paid to diagnose and treat breast cancer have responded by calling the new recommendations "reckless", "financially driven" and even "the first step in the rationing of healthcare." The simple truth is that there was never good data supporting the benefits of routine mammograms prior to age 50. The practice evolved within a system in which money flows when tests get done whether or not they are a good idea. Breast cancer screening is big business in the United States, and a recommendation to decrease the screening for it by at least 50% threatens a lot of incomes.

To be clear, there are women alive today because they got mammograms prior to age 50. In the information age, it is easy to locate stories of a woman saved by an early mammogram. It is more difficult to find the significant harm done by routine screening. For example, women younger than age 50 who have an "abnormal" mammogram go through significant psychological stress during the subsequent work-up which in the vast majority of cases shows no cancer. The work-up may include breast biopsies which involve pain, cost and some risk from the procedure itself. There is both a financial and distraction cost of all this that takes money and energy away from other public health needs such as decreasing the rate of heart disease which kills many more women than does breast cancer.

The most intuitive way to interpret the data surrounding mammograms is to look at the "Number Needed to Screen." Simply, this number tells us the number of women under age 50 we would need to screen with annual mammograms and for how many years in order to save a life. In the case of breast cancer, the Number Needed to Screen is approximately 2,000 women screened annually for 10 years. Therefore, we save one life for every 20,000 mammograms performed on women younger than age 50. Of these 2,000 women about 50% or 1,000 of them will have to endure the consequences of an "abnormal" mammogram during the 10 years. Another way of saying this is that for every 1,000 women under age 50 who have abnormal mammograms during the 10 years one life will be saved.

Admittedly, if you're that one life the statistics above don't concern you or your family. That logic is always (including this week) used to justify screening for rare problems. However, the problem with that logic is that it ignores the harm done to the thousands of women who get abnormal mammogram results but have no cancer. The logic also pretends that our resources are infinite and that screening for one disease has no effect on our ability to prevent other diseases. In fact, if the money spent on mammograms were directed to more pure prevention strategies (improved diet, decreased smoking, increased exercise, etc.) fewer women would die not only of breast cancer but of the other diseases caused by the same lifestyle problems (heart disease in particular).

We may not be too far away from the day when screening technology for breast cancer improves to the point where less harm would be done by screening younger women and the benefits would therefore outweigh the risks. However, at this point we're stuck with a screening method that exposes women to radiation, fails to detect small but aggressive tumors, and leads to a lot of false "abnormals." In this context, the task force's recommendations are right on target.