Breast cancer screening can risk 'needless treatment'

THOUSANDS of women could be getting complex and invasive treatment for breast cancer which they do not need because of "over-diagnosis" during screening, research suggested yesterday.

Scientists think that as many at 10 per cent of positive breast cancer screening results could be cases where the cancer would never have come to the attention of doctors during a woman's lifetime if it were not for screening.

This can result in invasive treatment such as surgery and radiotherapy which may never have been necessary if the woman had not attended breast screening.

However, cancer experts warned that women should not be put off getting tested.

Writing online in the British Medical Journal, a team of Swedish researchers said it was widely agreed that breast screening could reduce deaths.

But more discussion was needed on the negative side-effects of over-diagnosis, said Malmo University Hospital.

The team used data from a breast cancer screening trial in Sweden between 1976 and 1986.

The women who took part in the trial were followed until December 2001, to track survival and detection of breast cancer.

The researchers estimated that the rate of over-diagnosis of breast cancer was 10 per cent in women aged 55 to 69 who took part in the screening trial when comparing the incidence of cancer with a control group of women who were not screened.

The researchers said earlier studies looking at the problem of over-diagnosis had revealed rates of up to 54 per cent, but a more recent study had put it at 1 per cent. However, they said these previous studies were not based on direct observations like their research.

"It is widely agreed that screening using mammography can reduce mortality in breast cancer," they wrote. "The rate of over-diagnosis is another issue to be considered in the ongoing discussion about clinical and public health implications of breast cancer screening."

Another research team, also writing in the BMJ, said the information women are sent about breast screening needed to be more balanced so they know about the benefits and harms.

The researchers, from the Nordic Cochrane Centre in Copenhagen, said the organisers of publicly funded screening programmes faced a conflict of interest because they wanted uptake to be as high as possible.

They also said research suggested women generally exaggerated screening's benefits, but were unaware of the harms.

Cancer Research UK said the Swedish study was "interesting", but the charity's screening expert, Professor Stephen Duffy, cautioned: "Women should not be put off attending their screening appointment as the benefit of breast cancer screening outweighs any possible risk of having unnecessary treatment."