WIDER BREAST CANCER SCREENING WON'T BE A BOON TO WOMEN
New Scientist, 13 November 2014
CANCER screening sounds like the ultimate in preventive medicine. Spot a tumour early and it is easier to treat and cure.
That's the theory, anyway. But it ignores the potential problem of overdiagnosis – finding tiny tumours that would never have caused any harm, yet get treated aggressively. The big question for any programme is whether the harms outweigh the benefits.
This is answered most clearly for prostate cancer. Most trials show that men who have regular tests live no longer than those who do not. This evidence stopped the introduction of routine prostate screening in the UK.
There is now a growing body of evidence suggesting that breast cancer screening has the same shortcoming. Yet breast screening is an established part of many health systems. Anyone arguing for a rollback is up against entrenched interests.
In the UK, the government is actually considering widening the age range for breast screening despite growing evidence that it puts the age groups concerned at risk (see "Critics say wider breast screening trial 'unethical'"). The only way to get a reliable assessment of the idea is through a large clinical trial, which the UK is carrying out.
However, the information leaflet given to participants does not tell them they may be at higher risk of overdiagnosis. It does not even clearly state that they are part of a trial, a deficit of informed consent that breaches a basic tenet of medical research. Considering this is the largest ever randomised clinical trial, involving 3 million women, these omissions are shocking.
Attitudes may be changing. Earlier this year, the Swiss Medical Board said breast screening should cease altogether. And a recent report from UK MPs questioned the age extension.
The UK government does not have to accept the report, but it should use the opportunity to halt the trial until its many flaws have been addressed. At the very least, the information given to women needs to be corrected so that they are not being misled – or used as unwitting guinea pigs.
