Study: Breast Cancer Screening Fails to Reduce Advanced Cancer Incidence

Breast cancer screening does not reduce the incidence of advanced cancer and it results in overdiagnosis of the disease, according to a study published in the Annals of Internal Medicine.

Researchers from Denmark and Norway sought to assess the association between breast cancer screening and the stage of cancer detected, and to estimate the overdiagnosis of breast cancer. The study took place in Denmark from 1980 to 2010 and included women aged 35 to 84. Women in Denmark who participated in the Danish breast cancer screening programs from 1991 to 2010 were compared with those who lived in areas of Denmark that did not offer mammography screening.

The researchers assessed trends in the incidence of breast tumors that were advanced (larger than 20 mm) and nonadvanced (20 mm or smaller) in screened and nonscreened women. The researchers compared the incidence of advance and nonadvanced tumors among women aged 50 to 84 in screening and nonscreening areas and the incidence for nonadvanced tumors among women aged 35 to 49, 50 to 69, and 70 to 84 in screening and nonscreening areas.

The results showed that screening was not associated with lower incidence of advanced tumors. “The incidence of nonadvanced tumors increased in the screening versus prescreening periods,” they wrote. “The first estimation approach 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]). The second 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]).”

An accompanying editorial said that overdiagnosis resulting from breast screening should be recognized and accepted. "[C]onsidering all small breast cancer lesions to be deadly aggressive cancer is the "pathology equivalent of racial profiling," wrote Otis Brawley, MD, MACP, chief medical officer of the American Cancer Society. He suggested that the limitations to such screening programs be accepted and that ways to use screening more effectively be determined and implemented. He also wrote that the medical community should focus more on the message of breast cancer prevention through diet, weight control, and exercise.