Quantifying the Benefits and Harms of Screening Mammography

JAMA Internal Medicine, the journal of the American Medical Association, published the findings of a brief online survey of middle-aged Americans.Most had previously been screened for either breast or prostate cancer but about half said they would not choose to start screening if the test resulted in more than one overtreated person per one cancer death averted.

ABSTRACT

Quantifying the Benefits and Harms of Screening Mammography — The Journal of the American Medical Association, published since 1883, is an international peer-reviewed general medical journal published 48 times per year

Like all early detection strategies, screening mammography involves trade-offs. If women are to truly participate in the decision of whether or not to be screened, they need some quantification of its benefits and harms. Providing such information is a challenging task, however, given the uncertainty—and underlying professional disagreement—about the data. In this article, we attempt to bound this uncertainty by providing a range of estimates—optimistic and pessimistic—on the absolute frequency of 3 outcomes important to the mammography decision: breast cancer deaths avoided, false alarms, and overdiagnosis. Among 1000 US women aged 50 years who are screened annually for a decade, 0.3 to 3.2 will avoid a breast cancer death, 490 to 670 will have at least 1 false alarm, and 3 to 14 will be overdiagnosed and treated needlessly. We hope that these ranges help women to make a decision: either to feel comfortable about their decision to pursue screening or to feel equally comfortable about their decision not to pursue screening. For the remainder, we hope it helps start a conversation about where additional precision is most needed.
Cancer screening involves trade-offs. Screening offers the potential benefit of avoiding advanced cancer and subsequent cancer death. It also produces the harms of false alarms, overdiagnosis, and unnecessary treatment. Because different individuals value these benefits and harms differently, there is no single calculation to answer the question of what to do. Instead, each of us needs information about both the benefits and harms to arrive at our own decision.

Simply knowing that there are benefits and harms to screening is not sufficient to make the decision; information about their relative magnitude is essential. If 100 people benefit by avoiding a cancer death at the expense of the harms of 50 false alarms and 10 overdiagnoses with the ensuing unnecessary treatments, then the decision is easy. However, if for the same harms, the benefit is only 1 person avoiding a cancer death, the decision may be considerably more difficult. In this article we quantify the benefit-harm trade-off for screening mammography.