According to new research conducted in the Netherlands, mammography screening appears to have had a minimal effect on deaths from breast over the last 24 years.
The results found that screening is linked with up to 5% reductions in breast cancer mortality in women aged 50 and over, compared to improved treatments, which would be associated with a 28% reduction.
Futhermore, they found that overdiagnosis has steadily increased over time, with the extension of screening to women aged 70-75, and with the introduction of digital mammography.
Dating back to 1989, women in the Netherlands aged 50-75 have been encouraged to have mammography screening every two years. Screening was enlarged to women aged 70-75, starting in 1997, and digital mammography was introduced after 2006.
An assessment of the screening program, published in 1993, suggested moderate decreases in the incidence of some categories of advanced cancer from 1989 to 1997. Therefore, a team, led by Philippe Autier at the International Prevention Research Institute in France, undertook an update of the incidence of different stages of breast cancer among women of all ages in the Netherlands from 1989 to 2012.
They estimated the number of deaths from breast cancer that were avoided because of screening, and measured breast cancer overdiagnosis, defined as the number of breast cancers that would have never been detected during a woman’s lifetime in the absence of screening.
About one third (32%) of cancers found in women invited to screening in 2010-12 and about half (59%) of screen detected cancers would be overdiagnosed, they estimated.
The study did have some limitations that could have influenced the results. But the authors conclude that the Dutch mammography screening program seems to have little impact on the burden of advanced breast cancers, which suggests a marginal effect on breast cancer mortality.
Autier Philippe, Boniol Magali, Koechlin Alice, Pizot Cécile, Boniol Mathieu Effectiveness of and overdiagnosis from mammography screening in the Netherlands: population based study BMJ 2017; 359 :j5224
Image: U.S. Air Force/Airman 1st Class Andrew Lee