False-Positive Screening Mammograms: Good News, but More To Do

• False positive reactions
• Mammography
• Anxiety
• Patient compliance
• Mass screening

In the war against cancer, little progress has been made in preventing cancer occurrence. Except for cancer of the lung, we do not even know how to prevent most common cancers. Medical strategies, therefore, have been primarily aimed at treatment and, increasingly over the past few decades, screening for occult disease.

Screening has been most successful for cervical cancer, resulting in a 75% decrease in cervical cancer mortality rates from 1950 to 1994 (1). But the mortality rate from breast cancer is now beginning to decline as well, by 5.6% between 1990 and 1994 (1); the decrease is almost certainly due in part to increasing use of mammography. It is estimated that 70% of women 40 years of age or older (approximately 40 million U.S. women) have had screening mammography in the previous 2 years (2).

As with most medical interventions, bad effects come along with the good. An unintended adverse effect, and an integral part of any screening program, is the false-positive result—a positive result on a screening test in a patient without cancer. Clinicians who conscientiously incorporate cancer screening into their practices know all about false-positive results. Instead of stamping out cancer, they find their patients and themselves all too often caught up in anxiety-provoking and time-consuming follow-up tests that most often lead to naught. They are experiencing the results of the epidemiologic fact that when even a very sensitive and specific test is applied to the general population, most positive test results will be false because the prevalence of the cancer …