Women ages 50 to 69 years who attend mammography screening reduce their risk of dying from breast cancer by 40% compared with women who are not screened, according to a major international review of the latest evidence on breast cancer screening. This review was published in the New England Journal of Medicine (2015; doi:10.1056/NEJMsr1504363).

Overall, women who are invited to attend mammography screening have a 23% risk reduction in breast cancer death (owing to some attending and some not), compared with women not invited by routine screening programs.

The study states breast cancer is the most frequently diagnosed cause of death from cancer in women worldwide.

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Experts from 16 countries assessed the positive and negative impact of different breast cancer screening methods, based on a comprehensive analysis of evidence from 11 randomized controlled trials and 40 high-quality observational studies.

The latest findings were coordinated by the International Agency for Research in Cancer (IARC), the World Health Organization’s specialized cancer agency. The findings will contribute to an update of the IARC Handbook on breast cancer screening, last published in 2002.

The findings look at breast cancer screening on a global level and therefore take into account routine screening programs (where all women of a certain age are invited to attend) and opportunistic screening services (which operate in countries without a set program).

“This important analysis will hopefully reassure women around the world that breast screening with mammography saves lives. The evidence proves breast screening is a vital tool in increasing early diagnosis of breast cancer and therefore reducing the number of deaths,” said Professor Stephen Duffy of Queen Mary University of London in the United Kingdom about the findings.

The report confirms previous findings that women ages 50 to 69 years benefit most from breast cancer screening. However, several studies also showed a substantial reduction in risk of death from breast cancer by inviting women ages 70 to 74 years for screening, which is a shift away from previous consensus.

Only limited evidence in favor of screening women in their 40s was identified. The report stated that “the vote was almost evenly divided between limited and sufficient evidence,” regarding mammography reducing breast-cancer mortality in women ages 45 to 49 years.

The purpose of breast screening is to diagnose breast cancer in women earlier, therefore improving prognosis and reducing the number of late-stage cases and deaths. However, concerns have been raised over the negative impact of mammography screening, including false-positive results, overdiagnosis, and possibly radiation-induced cancer. This new review builds upon previous evidence that suggests the potential benefits of breast screening outweigh the risks.

In the several decades since breast cancer screening was identified as an effective method in reducing breast cancer deaths, mammography screening has been implemented in high-income countries, and less so in countries in central and Eastern Europe, whether as opportunistic or organized programs. Most countries in Latin America have national recommendations or guidelines. In other low and middle income countries, breast cancer screening is promoted primarily by advocacy groups and periodic campaigns to promote breast awareness.