European Study Sheds Light on Impact of Mammography Screening on Breast Cancer Morbidity

Breast cancer mortality appears to be decreasing not only in the United States but internationally as well. While mammography and screening supporters point to its efficacy as the main reason for this decrease, there is no definitive answer. With that in mind, Dr Philippe Autier, research director at the International Prevention Research Institute in Lyon, France, and colleagues sought to compare the trends in breast cancer mortality and the relative screening policies among 3 pairs of neighboring European countries.

Based on preset criteria, Autier and colleagues chose the following country pairs: Sweden and Norway, the Netherlands and Belgium, and Northern Ireland (United Kingdom) and the Republic of Ireland. The researchers leveraged information from published peer-reviewed articles and reports; they divided screening into 2 categories: those in which women of a defined age were regularly invited to screenings (ie, organized screenings) and those in which the screening was left to the discretion of the women and/or their doctors (ie, nonorganized screenings). Breast cancer mortality data were collected from the World Health Organization mortality database and from Belgium mortality statistics.  
 
The first country-pair examined was Sweden and Norway. Sweden had its organized mammography screening program implemented in 1986 following clinical trials in the 1970s and 1980s, while Norway initiated its organized screening in 1996. In Sweden all women between 50 and 69 years are invited into the program; nationwide coverage was reached in 1997 for this group. In addition, 60% to 70% of women aged 40 to 49 years are also invited. Screening attendance rates in Sweden are among the highest recorded in any country. In Norway, in contrast, all women aged 50 to 69 years are invited every 2 years, and nationwide coverage was achieved in 2005. Mortality rates decreased from 1989 to 2006 by 16.0% and 24.1% in Sweden and Norway, respectively.

A national organized mammography screening program was initiated in 1989 in the Netherlands, while in Belgium, screening was discretionary until 2001, at which time a national screening program was established. Nonorganized screening is uncommon in the Netherlands. In both countries, women aged 50 to 60 years are invited for screening every 2 years, but women aged 70 to 74 years have been invited since 1998 in the Netherlands. Since 1997, participation has been around 70% to 79% in the Netherlands. In comparison, participation was approximately 60% in Belgium by 2005. In both countries, breast cancer mortality decreased from 1989 to 2006, with greater increases in Belgium (25.0%) as compared to the Netherlands (19.9%).

Organized mammography was introduced in Northern Ireland in the early 1990s for women aged 50 to 64 years, with screening happening every 3 years. In comparison, organized screening began in Ireland in 2000, where women between 50 and 69 years are invited every 2 years. In 2008, coverage was 76% in the Republic of Ireland, while the rate has been hovering around 70% to 75% since 1995 in Northern Ireland. Similar breast cancer mortality rates have been seen from 1989 to 2006, with a rate of 26.7% in the Republic of Ireland and 29.6% reduction in Northern Ireland.

Interestingly, mortality began to decrease in Northern Ireland and the Netherlands shortly after the screening was introduced, but that mortality began to decrease years before the target groups were attending screening in Belgium, the Republic of Ireland, and Norway. Further, the authors noted the greatest reduction in breast cancer mortality occurred in young women (ie, women between 40 and 49 years). Overall, mortality rates varied little between countries, and Autier and colleagues believe that screening did not play a direct role in the reductions in breast cancer mortality.

“Improvements in treatment and in the efficiency of healthcare systems may be more plausible explanations [for reduced breast cancer mortality],” the researchers explained. “Our study adds further population data to the evidence of studies that have used various designs and found that mammography screening by itself has little detectable impact on mortality due to breast cancer.”

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References:

Reference
Autier P, Boniol M, Gavin A, Vatten LJ.Breast cancer mortality in neighbouring European countries with different levels of screening but similar access to treatment: trend analysis of WHO mortality database.  BMJ. 2011; 343:d441.