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Time for a new trial of breast cancer screening?

November 5, 2012

If I was a woman aged 50 with no particular family history, I’d steer clear of mammography. It might reduce my chance of dying from breast cancer by 20%, but it would increase my chance of being diagnosed and treated for it by 60%.  Three chances of being “given” breast cancer, for every one of being saved.  Click here for more.

But maybe I’m just a misguided man.  Many women queue up for mammograms.  Perhaps modern ones are more accurate, and cause fewer false positives.  Perhaps early treatment has got better.

Or maybe screening is less effective than we think. Treatment of clinically presenting breast cancer has improved since most of the trials were done. Hormone therapy is effective, surgery less mutilating, and chemotherapy and radiotherapy better than they used to be.  All else being equal, as conventional treatment improves, the benefit of screening must fall.   Think about it – if treatment after conventional diagnosis was 100% successful, screening could not possibly improve it.

If we’re honest there are so many uncertainties, and the benefit/harm ratio is so finely balanced, that many well-informed women would surely agree to randomisation.

The largest and best quality of the breast-screening trials, (UK Age 1991) recruited 150,000 women. In the UK about 300,000 women join the screening programme annually, and a bit over a million get a mammogram every year. A trial of 150,000 women is feasible.

Let’s do it.

Jim Thornton

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