Doubt has been cast on the value of screening women for breast cancer - but some doctors are deeply sceptical about cancer screening programmes in general.

Questioning the worth of screening is tantamount to heresy in much of the UK medical establishment.

Indeed, the government gave the national programme in England its vote of confidence on Friday by suggesting it is likely to be extended to women aged 65 to 69.

A succession of charities and experts also state their confidence in the programme.

And even one story of how a cancer deep in the breast was spotted by screeners is hard to ignore.

But some doctors suggest that the millions spent annually organising and carrying out population-wide screening for cervical and breast cancer would be better used funding extra research into treatments.

The central question is this - do the benefits of screening, the early detection of cancer, outweigh the potential harms?

Some argue that the chances of an individual woman suffering the anguish of an "abnormal" smear test, or an unnecessary operation to biopsy a lump detected by mammography, are greater than those of her survival chances being boosted.

The official statistics on breast screening boil down to this: for every 1,000 women screened, there is one fewer death from breast cancer.

Overall breast cancer mortality has dropped by 14% since the start of the screening programme a decade ago.

Whether this reduction is entirely due to screening detecting the cancer earlier is open to question - it may have been due to improvements in treatments since the screening programme was launched, or a natural decline in numbers.

Guiding principle

Dr Keith Hopcroft, an Essex GP, strongly opposes screening - both breast and cervical.

He says the guiding principle for doctors should be that their intervention "does no harm".

He said: "It's very traumatic to be one of the 25% of women whose smear comes back as abnormal. These women don't forget that for a long time.

"Many will end up having colposcopies, which are distressing, and can lead to psychosexual problems.

"And the vast majority of these will have no problems with cancer whatsoever."

'Disgust'

He added: "My personal view is that screening is a complete waste of time and money."

Professor Michael Baum, a professor of surgery at the Royal Free and University College London School of Medicine, is an authority on breast cancer, and is a former member of the National Screening Committee, which evaluates scientific evidence about the effectiveness of screening programmes.

He helped set up the breast cancer screening programme in the south east of England more than 10 years ago.

He resigned from the committee, "in disgust" he says, because he felt women were not being given enough information about the "downside" of screening to make an informed choice about whether to take part.

Once the risks of screening are weighed up, he says, he is "sceptical" whether breast screening is worthwhile.

'No axe to grind'

He said the study questioning screening - published in The Lancet - had "really let the skeletons out of the cupboard".

He said: "This was carried out by top-notch statisticians with no axe to grind.

"The trouble is, to be sceptical about screening in this country is to be in favour of sin, against virtue and anti-woman. I'm none of these things."

Modern doctors like the medicines and treatments they use to be backed by firm evidence that they are effective.

The breast screening programme did detect almost 4,000 small tumours in 1997/8, suggesting they had been caught early, increasing the chances of successful treatment.

And the cervical smear programme carried out almost 4m tests - with almost 150,000 showing borderline cell changes requiring a repeat smear. More than 3,600 patients turned out to have cancer.

But the exact impact of the screening programmes on women's health is hard to evaluate.