Breast cancer screening benefits outweigh harms
MedWire News: The benefits of mammography, in terms of lives saved, significantly outweigh any harm experienced in the form of overdiagnosis, a study based on data from England and Sweden has shown.
Prue Allgood (Wolfson Institute of Preventative Medicine, London, UK) and colleagues analyzed breast cancer incidence and mortality data from a major randomized trial conducted in Sweden and from the general female population in England before and after the initiation of the UK National Breast Screening Programme.
They then compared these data with an estimate of the absolute numbers of tumors overdiagnosed through breast screening. The researchers found that there was substantial and significant reduction in breast cancer mortality associated with screening in both the Swedish Two-County Trial and the English patients in the UK program.
The absolute benefits were estimated as 8.8 and 5.7 breast cancer deaths prevented per 1000 women screened for 20 years starting at age 50 years from the Swedish and English cohorts, respectively.
The corresponding estimated numbers of cases overdiagnosed per 1000 women screened for 20 years were 4.3 and 2.3 in the Swedish and English cohorts, respectively.
This means that one overdiagnosed case would be expected for every two breast cancer deaths prevented in the Swedish group. Or for every 11 cases diagnosed, two lives will be saved, and one case will be overdiagnosed.
For every two breast cancer deaths prevented in the English program, the team estimated that there were fewer than one overdiagnosed patients. Thus, for approximately every 28 cases diagnosed, 2.5 lives were saved, and one patient was overdiagnosed.
“The benefits in terms of numbers of deaths prevented are around double the harms in terms of overdiagnosis,” write Allgood and co-authors in the Journal of Medical Screening.
They conclude: “The benefit of mammographic screening in terms of lives saved is greater in absolute terms than the harm in terms of overdiagnosis.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010
By Laura Dean