Benefits and harms of mammography screening.

Magnus Løberg,Mette Lise Lousdal,Michael Bretthauer,Mette Kalager

doi:10.1186/s13058-015-0525-z

Abstract

Mammography screening for breast cancer is widely available in many countries. Initially praised as a universal achievement to improve women's health and to reduce the burden of breast cancer, the benefits and harms of mammography screening have been debated heatedly in the past years. This review discusses the benefits and harms of mammography screening in light of findings from randomized trials and from more recent observational studies performed in the era of modern diagnostics and treatment. The main benefit of mammography screening is reduction of breast-cancer related death. Relative reductions vary from about 15 to 25% in randomized trials to more recent estimates of 13 to 17% in meta-analyses of observational studies. Using UK population data of 2007, for 1,000 women invited to biennial mammography screening for 20 years from age 50, 2 to 3 women are prevented from dying of breast cancer. All-cause mortality is unchanged. Overdiagnosis of breast cancer is the main harm of mammography screening. Based on recent estimates from the United States, the relative amount of overdiagnosis (including ductal carcinoma in situ and invasive cancer) is 31%. This results in 15 women overdiagnosed for every 1,000 women invited to biennial mammography screening for 20 years from age 50. Women should be unpassionately informed about the benefits and harms of mammography screening using absolute effect sizes in a comprehensible fashion. In an era of limited health care resources, screening services need to be scrutinized and compared with each other with regard to effectiveness, cost-effectiveness and harms.

Highlights

The verb 'to screen' is defined as 'to sift by passing through a screen' [1]
Overdiagnosis does apply to both carcinoma in situ and invasive cancer; the lifetime risk of progression of carcinoma in situ to invasive breast cancer is unknown, but probably less than 50%; [40] and the lead-time is longer for in situ than invasive cancers
Based on different meta-analyses and reviews of benefits and harms of mammography screening [9,22,32] and our best estimate [19,34,35], we present a figure showing the different estimates of overdiagnosis and prevented deaths from breast cancer (Figure 3)

Summary

Introduction

The verb 'to screen' is defined as 'to sift by passing through a screen' [1]. 'To 'sift'; derives from an old Dutch word ('zeef'); a 'utensil consisting of a circular frame with a finely meshed or perforated bottom, used to separate the coarser from the finer particles of any loose material' [1]. For early detection by screening to be beneficial, we anticipate a continuous, linear growth pattern of tumors, and that breast cancer has not spread at the time when tumors are detectable at mammography. The idea of early detection started in the US in the early 20th century with educational mass campaigns where the message of 'do not delay' seeking medical help for a variety of cancer signs and symptoms was central [7]. None of these early campaigns had an effect on the mortality of breast cancer [8]. Løberg et al Breast Cancer Research (2015) 17:63

There should be an agreed policy on whom to treat as patients

Findings

Conclusion