The researchers theorized that if mammography is beneficial, it would lead to a decrease in late-stage breast cancer casesthe theory being that early detection prevents late-stage disease.
But the researchers did not find a reduction in late-stage disease in women who'd been offered screening. They did find, though, a substantial amount of overdiagnosis; among the 7,793 women diagnosed with breast cancer through participation in the screening program, 15% to 25% were overdiagnosedbetween 1,169 and 1,948 women. Based on those numbers, they further estimated that, for every 2,500 women invited to screening, 2,470 to 2,474 will never be diagnosed with breast cancer and 2,499 will never die from breast cancer. Only one death from breast cancer will be prevented. But 6 to 10 women will be overdiagnosed, and treated with surgery, radiation therapy, and possibly chemotherapy without any benefit.
Other HSPH authors included senior author Rulla Tamimi, assistant professor in the Department of Epidemiology, and Hans Olov-Adami, professor of epidemiology.
Support for the study was provided by the Norwegian Research Council and Frontier Science.
|Contact: Marge Dwyer|
Harvard School of Public Health