Friday, July 10, 2009

Breast cancer screening: everybody hurts

'The question is no longer whether breast cancer overdiagnosis occurs, but how often it occurs' says an editorial yesterday's British Medical Journal.

Many women it appears are having unnecessary chemotherapy, surgery and other treatments for breast cancer. This is unpleasant and dangerous for them, a waste of money for the NHS and misleads the rest of us about what modern medicine can really do. The apparent rise in breast cancer is, it appears, linked not to a real rise in breast cancer but to a rise in breast cancer screening.

The problem is that breast cancer screening - the mammogram - is not sophisticated enough. It cannot tell - and nor can the docs - whether the tumours it detects are life-threatening or not. You might argue that it's good to err on the safe side. The problem is there isn't a safe side.

Patients tend to be pro-screening. Ask a cancer patient and they'll demand screening on the grounds that it might well have picked up their cancer sooner. Ask the family of a dead cancer patient and they'll be even more vehement.

It's understandable but it makes no sense if screening is not possible. The MHF does not call for prostate cancer screening because there are no screens currently available that don't carry the risk of overdiagnosis. The same appears to be the case with breast cancer - and to quite a shocking degree. The research into overdiagnosis in several countries including the UK concludes that one in three breast cancers detected in a population offered organised screening is overdiagnosed.

Of course, every case is different and nobody is calling for the end of the mammogram. Overdiagnosis particularly affects older women because they have slower growing tumours and fewer years of life ahead - a point that isn't particularly well-covered in the press today and may lead to younger women making poor treatment decisions. But at medical school all students are taught on day one: first do no harm. That's why the NHS recently scrapped its leaflet inviting women to have a mammogram.

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