Researchers give mammography another vote of no confidence

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Mammography is a screening tool designed to diagnose breast cancer earlier than it other would be, which should lead to earlier, better and more effective treatment. Well, that’s the theory anyway. But as with the case with many things, theory does not always translate smoothly into practice. There has been for some years now growing doubts about the value of mammography. Two charges that have been made by some researchers is that mammography actually isn’t very effective at saving lives, and at the same times leads to more women being subjected to investigation and treatment for breast cancers that would never have been an issue if left alone.

And one more criticism has been that women have generally not been fully informed about the pros and cons of mammography. This means that most women have simply not been given the opportunity to make truly informed decisions about whether or not to have a mammogram. For more about the issues surrounding mammography, see here and here.

This week saw the publication of another study which sought to gauge the effectiveness of mammography. The study, published in the New England Journal of Medicine, assessed the outcomes of more than 40,000 women with breast cancer. Access to screening was associated with a 28 per cent reduction in risk of dying from breast cancer. This outcomes looks quite good on the face of it. However, breast cancer is one condition for which treatments have improved quite considerably in recent times. This means that at least some of the benefits associated with mammography may come from improvements in breast cancer care that have coincided with mammography screening.

This study found that in women who were not screened, mortality from breast cancer fell considerably too. It turns out that only about a third of the 28 per cent reduction in risk of death associated with mammography was down to mammography per se. In other words, this study found that mammography was associated with a reduced risk of death of breast cancer of about 10 per cent.

10 per cent might sound worthwhile, but how big the real benefits are depend on how likely women are to die from breast cancer. If, say, a woman’s risk of dying from breast cancer over a 10-year period is 10 per cent, then mammography (according to this study) would be expected to reduce this to 9 per cent (a 1 per cent reduction).

An accompanying editorial [2] puts the real figures into some perspective. If 2,500 women aged 50 were screened with mammography, only ONE will avoid dying of breast cancer. Now, many of these women (as many as 1000) will have to endure the potential stress of being told by their doctors that there’s something suspicious on their mammogram. And about 500 of these will go on to have a biopsy – an invasive procedure around which there is usually considerable anxiety. As a result of biopsy, it is estimated that between 5 and 15 women will be treated unnecessarily for a condition that was never going to bother them.

While mammography still has ardent support in some quarters, mounting evidence suggests it really is less beneficial and more hazardous than women have been led believe.

Out of curiosity I recently asked my 77-year-old mother (a retired doctor) if she’d ever had a mammogram. ‘No’ she replied, and in a way that said ‘why would I want to do that?’. Perhaps mothers do know best, sometimes.


1. Kalager M, et al. Effect of Screening Mammography on Breast-Cancer Mortality in Norway. N Engl J Med 2010; 363:1203-1210

2. Welch HG. Screening Mammography — A Long Run for a Short Slide? N Engl J Med 2010; 363:1276-1278

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