Breast cancer screening is linked to several harms such as the increased likelihood of having a mastectomy and receiving radiotherapy according to research published today.
The benefits and negative effects of seven breast screening programs were studied by researchers at the Nordic Cochrane Centre in Denmark ,on 500,000 women in Canada, the US, Scotland and Sweden.
Their study revealed that for every 2,000 women invited to have mammograms over a 10-year period, one would have their life prolonged but 10 would endure potentially devastating and unnecessary treatment.
Although overall screening appeared to reduce mortality by about 15 per cent, there was also an increase in the number of mastectomies by 20 percent as well as the likelihood of radiotherapy.
The research, however, has been questioned by the NHS breast screening program, which provides free breast screening for women over 50 every three years.
It issued a statement which said that the Department of Health's advisory committee on breast cancer screening had carried out a comprehensive evaluation of the program and found that for every 2,000 women joining it over 10 years, five lives would be prolonged.
According to Julietta Patnick, the director of NHS cancer screening programs breast screening saved 1, 400 lives each year and that women who were screened were also less likely to have a mastectomy than those who were not screened.
She said, "For lives to be saved, breast screening must detect cancers in the early stages. The benefits of breast screening far outweigh the risks and I would strongly encourage all women to make an informed choice to attend screening when invited."
The director of the Nordic Cochrane Centre, Dr Peter Gotzsche, said that another study which was done at the centre involved the analysis of letters and leaflets,Ž including ones from the NHS where women were invited to undergo a breast cancer screening.
He alleged that they tended to be biased and that the negative effects, such as overtreatment and overdiagnosis were not mentioned.
Dr Gotzsche said that following his study of breast cancer screening for seven years he was "amazed" at how emotive the issue was.
He said, "It has somehow become pretty religious. Some people get offended if you start questioning the balance between benefits and harms. They just don't want it discussed. This is an awkward position. It is wrong to not to inform women about the harms."
According to Dr Gotzsche the NHS statement which said that screening led to a reduction in the number of mastectomies was misleading.
Another long-term critic of screening, Professor Michael Baum, called for an independent assessment of the National Institute for Clinical Excellence, similar to that of breast cancer drugs arimidex and herceptin.
He said, "I think it is just for political reasons that screening is not subjected to the same intense scrutiny, Can you imagine any government closing it down?"
He added there was a huge industry that would "lose a hell of a lot of face if they began questioning the value of screening".