Danish study challenges value of screening mammography, draws sharp criticism from U.S. orgs

 - mammography patient

European researchers have reviewed a huge mammography dataset and found no association between screening mammography and a reduction in the incidence of advanced breast cancer.

The team drew their data from two comprehensive cancer registries in Denmark plus the medical records of all women in that country who had invasive breast cancer between 1980 and 2010.

Their study was published Jan. 10 in Annals of Internal Medicine.

Karsten Juhl Jørgensen, MD, of the Nordic Cochrane Centre and the University of Copenhagen and colleagues first compared the incidence of advanced tumors in women aged 50 to 84 living in regions of Denmark that regularly screened for breast cancer with such incidence in regions that did not do so.

From this they found that 271 invasive breast cancer tumors and 179 ductal carcinoma in situ (DCIS) lesions were overdiagnosed in 2010 (overdiagnosis rate of 24.4 percent [including DCIS] and 14.7 percent [excluding DCIS]).

Next they compared the incidence for nonadvanced tumors among women aged 35 to 49, 50 to 69, and 70 to 84 years in screening and nonscreening areas.

This approach, which accounted for regional differences in women younger than the screening age, found that 711 invasive tumors and 180 cases of DCIS were overdiagnosed in 2010 (overdiagnosis rate of 48.3 percent [including DCIS] and 38.6 percent [excluding DCIS]).

Further, the team found the incidence of nonadvanced tumors increased in the screening versus prescreening periods (incidence rate ratio, 1.49 [95 percent confidence interval, 1.43 to 1.54]).  

“Breast cancer screening was not associated with a reduction in the incidence of advanced cancer,” Jørgensen and co-authors conclude. “It is likely that 1 in every 3 invasive tumors and cases of DCIS diagnosed in women offered screening represent overdiagnosis (incidence increase of 48.3 percent).”

The American College of Radiology (ACR) and the Society of Breast Imaging (SBI) immediately responded to the study and its conclusions.

“Mammography overdiagnosis conclusions stated in Jørgensen et al. … are not supported by patient-specific data or even the data in the Jørgensen study as written,” ACR and SBI write in a news release sent by ACR. “The Jørgensen paper is not based on direct patient data that shows which women had a mammogram (at what frequency) and which did not.”

Click here for the study (abstract only without subscription) and here for the full ACR/SBI response.

For point-by-point refutations and criticisms of the study from SBI, click here and here