Mammography Screening Does Not Reduce Mortality

A new study finds that mammography screening is not associated with a reduction in breast cancer mortality, suggesting that the decline is due to better treatment, and not screening.

Researchers at Aarhus University Hospital (Denmark) and the University of Oslo (Norway) conducted an open‐cohort study to estimate the effect of organized mammography screening on incidence‐based breast cancer mortality. To do so, the researchers compared changes in mortality among all Norwegian women aged 30-89, identifying those who developed breast cancer in the period 1987-2010, before subsequently comparing the number of deaths before and after the Norwegian national breast cancer screening program was introduced in 2004.

The researchers used birth cohorts (1896‐1982) to construct three age groups in both the historical and screening period: women eligible for screening, and younger or older women that were ineligible for screening. An estimated relative incidence‐based mortality rate ratio (MRR) was then used to compare temporal changes in eligible women to concurrent changes in ineligible women. The results showed that all three age groups experienced an equal reduction in mortality. The study was published on August 25, 2018, in the International Journal of Cancer.

“The original randomized trials examining breast cancer screening were conducted way back in the 1980s, and they showed an effect,” said senior author Henrik Støvring, MD, of Aarhus University. “But the fact is that the better the treatment methods become, the less benefit screening has. The women who are invited to screening live longer because all breast cancer patients live longer, and they do so because we now have better drugs and more effective chemotherapy.”

The debate over the need for screening mammography in middle aged women has raged since 2009, when the U.S. Preventive Services Task Force (USPSTF, Rockville, MD, USA) recommended that routine mammography for women aged 40-49 should not be performed, as cancer risk is low, while the risk of false–positive results and overdiagnosis and overtreatment is high. In fact, the issue of overdiagnosis is a growing problem in all Western countries, where national screening programs are prevalent.

Related Links:
Aarhus University Hospital
University of Oslo