Polarized arguments about breast screening are not helping women, warns expert

Klim McPherson, Professor of Public Health Epidemiology at the University of Oxford looks at the evidence and calls for dispassionate analysis of all available data.

The burden of breast cancer is unremitting and we must do anything we can to contain it, he says. But screening for a progressive disease is justified only if earlier diagnosis and treatment improve disease progression.

A recent US report on screening for breast cancer estimated that the mortality reductions attributable to breast screening are 15% for women aged 39-49, 14% for those aged 50-59, and 32% for those aged 60-69. Worse still, estimated numbers of women needed to be invited to a US screening programme in order to save one life are high. For the younger group it is nearly 2,000 while in those aged 60-69 it is still nearly 400. In the UK, the figure is 1,610 for women aged 40-55.

A recent analysis from the Nordic Cochrane Centre also claimed that one in three breast cancers detected in screening programmes is overdiagnosed, although others argue that the lives saved by screening greatly outnumber overdiagnosed cases.

So are women more likely to be overdiagnosed than to have their life saved by screening mammography, asks McPherson?

Whatever we believe about the science, there is no doubt that screening for breast cancer has limited benefit and some possibility of harm for an individual women and marginal cost effectiveness for a community, he says. So, has the time come for a serious scientific rethink of the benefits of the NHS screening programme in the context of cost effective care?

Arguments that polarise are unhelpful and render women, many with strong preferences, more helpless, he argues. For too long they have been misled and confused by too much agenda driven analyses of these data. What is required now is a full examination of all the data by dispassionate epidemiologists to get the best estimates in the UK screening setting.

Meanwhile, he believes that the NHS screening programme needs to be really clear about these uncertainties when communicating with women, and organisers of current trials need to be clear about how much of this uncertainty will be addressed, with what precision, and by when. "More importantly, we all need to understand better how a national programme of such importance could exist for so long with so many unanswered questions," he concludes.