Have ‘up to 270 women died’ by missing a breast screening appointment letter?

David Spiegelhalter
May 3, 2018 · 4 min read

It was announced yesterday that, between 2009 and 2018, a coding error meant that 450,000 women aged around 70 in the UK were not sent their final breast screening appointment letter. These women were mistakenly not offered screening that may have picked up a cancer that had developed since their last screen 3 years before. Secretary of State for Health Jeremy Hunt announced in Parliament that “there may be between 135 and 270 women who had their lives shortened”. This has been reported as ‘up to 270 women died’.

Headline in Guardian

Presumably this is an estimate of the number of women who would have been diagnosed at this final screen, and would subsequently have benefited from the screening (see end for back-of-envelope calculations). There are three reasons why this claim is misleading.

First, he said this was the number of women who ‘had’ their lives shortened. But this is not strictly accurate — few of these women will have actually died of their breast cancer yet, as only around 15% of 70-year-olds diagnosed with breast cancer die of their disease within 5 years.

But they may have benefited from being diagnosed earlier, and this estimate is presumably based on a statistical model of what might happen in the future. Jeremy Hunt might better have said “there may be between 135 and 270 women who have had their life expectancy shortened”, although this probably would not have prevented the exaggerated headlines. [Note added on 3rd May: I now understand that it is feasible that up to 270 women may have already died earlier than had they been screened, but this would only be under multiple worst case assumptions].

Second, even a claim of reduced overall life expectancy would be questionable, as Hunt made clear in his announcement but which remained unreported. There is only weak evidence that screening helps prolong life, particularly for older women — there’s a reason that the screening programme ends at aged 70.

Of course all these statistical statements about life expectancy are about large groups of people and may sound rather cold. It’s a tragedy for any particular woman to have missed her cancer being detected earlier because of an administrative error, and so Jeremy Hunt is right to be abject with his apology.

But the third issue is that, contrary to popular belief, screening also does harm — the current leaflet states that, for every 200 women attending screening between 50 and 70, we would expect one to have her early death from breast cancer prevented, but three to be unnecessarily treated for a harmless cancer that would not have troubled them. It might be worth pointing out that these women (or their doctors) would never know this— they would forever be grateful, thinking that their lives had been saved by the harrowing treatment process. So it is an invisible harm, difficult to quantify or take into consideration.

But it means that up to 800 women may have been saved from harm by not sending them their final screening appointment letter, as they avoided possible reduction in their life expectancy through unnecessary treatment.

I feel very sorry for the women who missed getting a screening letter and have subsequently been diagnosed with cancer, or even died. Their situation is bad enough without them, and their families and friends, feeling they could have been helped if only they had received that letter. But this will only be true for a small proportion, and nothing will be said to the far larger number of (unidentifiable) women who would otherwise have faced diagnosis and treatment for a condition that would never have harmed them.

There’s a complex story behind these headlines, but there is no doubting that Jeremy Hunt needed to make a strong apology: there was a policy to offer women this screening choice and 450,000 were denied it by a mistake. It may have done harm to some and benefit to others — we’ll never know who, or how many, had which. Unfortunately, this will probably become known as the scandal that caused ‘up to 270 deaths’.

Back-of-envelope reality check (added 10.15, 3rd May)

The cancer screening leaflet estimates that of 200 women screened every 3 years between 50 and 70 (say 7 times), one will have an early death from breast cancer prevented. Very roughly, that’s 1 in 1400 women having their death from breast cancer prevented per screen (the final screen will presumably yield more breast cancers as they are older, but less severe).

If 450,000 people missed a final screen, then very roughly 450,000/1,400 = 321 women die early from breast cancer.

But only around 70% go for screening, so that’s around 321 x 0.7 = 225. This is in the 135–270 range quoted by Hunt, although this presumably comes from proper modelling rather than a three-minute analysis.

The leaflet also say that for every woman having an early breast cancer death prevented, three will be unnecessarily treated. So very roughly, up to 800 women may have benefited substantially from not being sent the letter.

Thanks to Alex Freeman

David Spiegelhalter

Written by

Statistician, communicator about evidence, risk, probability, chance, uncertainty, etc. Chair, Winton Centre for Risk and Evidence Communication, Cambridge.


The Winton Centre for Risk and Evidence Communication is hosted within the Department of Pure Mathematics and Mathematical Statistics in the University of Cambridge. Transparent evidence designed to inform, not to persuade.

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