ACR, SBI: Mammo Overdiagnosis Study Flawed

The analysis used in a recent study that found about 15 percent to 25 percent of breast cancers are overdiagnosed by mammogram was flawed, leading to an overestimate of overdiagosis and invalid conclusions about mammography’s value, according to The American College of Radiology and the Society of Breast Imaging.

The Annals of Internal Medicine study found that for every 2,500 women who were invited to be screened, 2,470 to 2,474 will never be diagnosed with breast cancer and 2,499 will never die from breast cancer. On the other hand, six to 10 women will be overdiagnosed and be treated for breast cancer that may never have needed treatment to begin with.

However, the Norwegian screening program, on which the study is based, is too new for researchers confidently to draw conclusions about effectiveness and side effects of mammography, the ACR and SBI said in a statement.

“Fortunately, there are randomized controlled trials with long-term follow-up, and national programs that introduced population-based screening much sooner than Norway, from which there are much better and more trustworthy estimates of mammography screening performance,” the groups stated.

The ACR and SBI pointed to two examples of such trials, including the Two-County Trial in Sweden, which used 29-year-follow-up data to estimate that there are 7.5 to 10 deaths prevented among 2,500 women invited to be screened every two to 2.5 years for 10 years.

“The more robust, more mature, and more carefully analyzed data not only prove the life-saving benefits of mammography screening,” the groups stated, “but also indicate a much smaller frequency of harms (including overdiagnosis) than what is suggested by Kalager et al.”