Breast screening programme in the UK criticised
The national breast screening programme may be harming more women than it helps, according to evidence presented to an official review.
A prominent international specialist has recommended that the national screening programme should be scrapped.
Prof Peter Gotzsche said 10 women are harmed by unnecessary treatment for every woman saved.
His views have been described as "gravely mistaken" by one doctor involved in screening.
Prof Gotzsche, who holds the chair of clinical research design and analysis at the University of Copenhagen, is part of the Cochrane Collaboration, an international network of medical specialists.
He said: "Screening detects a lot of cancers that are not dangerous. We call them overdiagnosed cancers, they are pretty harmless.
Mr Kieran Horgan from the Breast Surgery Association
We see a number of ladies who have breast cancer diagnosed through screening. Being a little older, I've been in practice since the start of the programme and I've seen it develop over the years. The ability of the radiologist to say what is important or not when they look at mammograms has improved beyond all measure. If you take 1,000 women who have a mammogram each year, 0.85 end up with an operation for a benign tumour. The hope would be nobody but that is an extremely good accuracy rate. When I started as a trainee, frequently 12 or 14 women would go into surgery and have a lump removed in order to know if one of them had a breast cancer. That no longer happens, 98% of women who come through screening with one visit and biopsy come to us in the breast surgery service with a diagnosis already made. So they are very significant advantages.
"But many of these are treated by a mastectomy so when you introduce screening, you have more mastectomies. So seen over longer there are more mastectomies in the screened areas.
"So women have seriously been misinformed throughout 30 years. It's a public health scandal."
The screening programme has been defended by those involved in carrying it out.
They concede that it is not a perfect science, but insist it does save lives.
Prof Andy Evans of Ninewells Hospital in Dundee said: "There is a high false positive rate because trying to tell a small cancer from a bit of normal tissue is ridiculously difficult and we can only do it as well as we do, if we read 5,000 films a year, go on lots of training and have our performance assessed on a regular basis.
"We are probably the best policed and audited group of doctors in the UK and so it's a fault of the technology that screening mammography is in no way perfect, far from perfect but it saves lives and it is the best we have at the moment."
Prof Evans disputes Prof Gotzsche's assessment of the proportion of "false positives".
He added: ""In my opinion you save at least two women's lives for every one case you over-diagnose.
"I think if we stopped the programme literally thousands of women would die of breast cancer completely unnecessarily and I think he is gravely mistaken."
About two million women are screened every year in the UK.
The review into the effectiveness of the breast screening programme was commissioned by Cancer Research UK and the Department of Health and is due to report back on Tuesday.
The Scottish government says it will consider any recommendations that are made.
A BBC Scotland investigation into the breast screening programme is broadcast on Sunday 28 October at 16:30 on BBC Radio Scotland.