The Breast Screening Review: evidence and recommendations


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Sir Michael Marmot
Institute of Health Equity, University College London, UK

Abstract

The NHS Breast Cancer Screening Programme in the UK currently invites all eligible women aged 50-70 years for a screening mammogram every three years. Since the screening programme was established, there has been debate, which has become sharply polarized, over the magnitude of benefit and of harm, and the balance between them. The major benefit is reduction in mortality from breast cancer; the major harm is over diagnosis and its consequences.

Professor Sir Mike Richards, National Clinical Director for Cancer and Dr Harpal Kumar, Chief Executive Officer of Cancer Research UK asked Sir Michael Marmot to convene and chair an independent panel to carry out a rigorous review of the evidence on benefits and harms of breast screening. The Panel reviewed the extensive literature and heard testimony from experts in the field.

The purpose of screening is to advance the time of diagnosis. A result of this is to increase the apparent incidence of breast cancer and to extend the time from diagnosis to death, even were screening to confer no benefit. The appropriate measure of benefit, therefore, is mortality from breast cancer in women offered screening compared to women not offered screening. The Panel reviewed evidence from randomized controlled trials, meta-analyses, and observational studies.

The major harm of screening which the panel looked at was that of overdiagnosis. Given that the definition is the excess number of cancers diagnosed by screening that would not have come to attention in the woman's life time, there is need for long follow up to assess the magnitude of overdiagnosis.

In this lecture, Sir Michael Marmot reports the panel's conclusions, reflects on the nature of the evidence reviewed by the Panel, and discusses the recommendations.