Evidence based mammography screening: is evidence changing?

U A Liyanage,U M J E Samaranayake

doi:10.4038/sljs.v37i2.8625

Abstract

Population-based mammography screening programmes were launched by developed countries in the latter half of the twentieth century based on the promising evidence on mortality benefits reported by the earliest randomised control trials (RCTs). It was widely accepted that screening mammography significantly reduced breast cancer mortality in women invited for screening. However, since the first RCT in the 1960s, varying evidence has been tabled by many researchers, sometimes alarming the public, drawing attention to the harms of screening mammography, mainly identified as overdiagnosis and false positives. While overtreatment is recognised as a consequence of over diagnosis, a relatively newer set of harms categorized under psychological distress have been highlighted as resultant from false positive screening tests. Currently, the magnitude of the harms of screening mammography remains uncertain. The most turbulent reviews on breast screening, however, were the queries into the well and long believed mortality benefits of mammography screening first tabled in the 1970s by the Canadian national breast screening study. A Cochrane review by Gotzsche and Jorgensen further added to the negative attributes of mammography screening as they concluded that the actual current mortality benefits are nonsignificant and smaller than that claimed by many RCTs which were poorly randomised. Although heavily criticized, sparks ignited by these reports have led many countries worldwide to conduct their panel discussions on evidence on population screening mammography. While many countries have decided to continue their programmes understanding the harms involved, Switzerland in this light has discontinued their population-based mammography screening programme. The debate continues; currently while not overlooking the mortality benefits of mammography, it is also understood that the mortality benefits are not solely due to mammography but are also contributed by other factors such as advancement in therapeutic measures and awareness on breast cancer created among the females. In this regard, critical evaluation of global literature is imperative to make country-specific policy decisions for middle-income countries such as Sri Lanka, who are contemplating the options for expanding opportunistic mammography screening services to reach wider population screening targets.

Highlights

Critical evaluation of global literature is imperative to make country-specific policy decisions for middle-income countries such as Sri Lanka, who are contemplating the options for expanding opportunistic mammography screening services to reach wider population screening targets. In the latter half of the 20th century, many developed countries invested in population-based mammography breast cancer screening programmes with varying national policies between countries
Embarking on mass screening mammography occurred as recommended by world's leading guideline groups, largely supported by the scientific evidence which was tabled at that time highlighting the mortality benefits of screening mammography
Some authors have sceptically expressed this association, which is common to many other cancers with specific screening programmes, 'as if screening was causing cancer' because a paralleled rise in incidence was not seen in control groups in randomized trials [1]. This rise in breast cancer incidence was marked among women of perimenopausal age group, who were the main participants at mammographic screening programmes

Summary

Introduction

In the latter half of the 20th century, many developed countries invested in population-based mammography breast cancer screening programmes with varying national policies between countries. The results of this trial which evaluated benefits of mammography and clinical breast examination were first reported in 1966 followed by updates in 1971 and 1982 which showed a reduction of breast cancer mortality rates in the intervention group over controls [2].

Results

Conclusion