ACR Disputes NEJM Study Claiming Mammo Overdiagnosis

November 24, 2012

Mammography screening overdiagnoses women who may never have had clinical symptoms, finds a study the ACR said is incorrect and misleading.

Routine mammography screening results in overdiagnosis of breast cancer, diagnosing women who may never have had clinical symptoms, according to a study published in the most recent issue of the New England Journal of Medicine. However, the American College of Radiology argued the thesis of the article was incorrect and misleading.

The study authors searched through Surveillance, Epidemiology, and End Results data to examine trends from 1976 through 2008 for incidence of early-stage breast cancer (ductal carcinoma in situ and localized disease) and late-stage breast cancer (regional and distant disease) among women 40 years of age or older. Their findings revealed detection of early-stage breast cancer doubled from 112 to 234 cases per 100,000 women, an absolute increase of 122 cases per 100,000 women. Late-stage diagnosis decreased by 8 percent though, from 102 per 100,000 women to 94 cases per 100,000, an absolute decrease of 8 cases per 100,000 women.

The authors determined that only eight of the additional 122 additional early-stage cancers that were diagnosed were expected to advance to advanced disease. After adjusting for excess incidence associated with hormone-replacement therapy and trends of incidence in breast cancer in women under 40 years old, the authors determined that over the past 30 years, breast cancer was overdiagnosed in 1.3 million women. In 2008 alone, they estimated that 70,000 women (31 percent) were overdiagnosed with breast cancer.

The ACR claimed that the article was “deeply flawed and misleading” and based on false assumptions. According to the numbers provided by the ACR, the incidence was incorrectly determined:

“The authors suggest that the baseline incidence of breast cancer would have increased by 0.5 percent each year, when in fact, the data show that it would likely have increased by twice that amount,” the organization said in a statement. In 1980, before routine mammography screening, the incidence of breast cancer was 100 in 100,000 women, up from 60 in 100,000 in 1940. “If there had been no screening, and the rate continued to increase as it had for 40 years, the incidence in 2008 would have been over 130/100,000,” according to the ACR.

The overdiagnosis claimed by the study authors is more realistically the treatment of ductal carcinoma in situ (DCIS) that has reduced the incidence of invasive breast cancer, the ACR noted. “This is in addition to the observed 30 percent reduction in deaths each year due largely to screening.” The ACR stated that the authors failed to recognize that a reduction in advanced stage disease is not required to have a reduction in deaths from screening.

The ACR concluded that the study’s thesis was wrong, stating: “Misleading articles, based on fault assumptions and methodology are counterproductive. If such misinformation is used to determine screening guidelines and recommendations, the cost may be lost lives.”