COPENHAGEN, DENMARK. Medical researchers at the Nordic Cochrane Centre have reached the surprising conclusion that "screening for breast cancer with mammography is unjustified". The researchers reviewed eight randomized trials aimed at determining the effect of mammography screening on mortality from breast cancer. The trials carried out in the United States, Canada, Scotland, and Sweden involved over 500,000 women. A careful study of the design of the trials showed that six of them were biased in a direction that would tend to exaggerate the benefits of mammography. In some of the trials the women in the screening group were significantly younger than those in the control group. In others the screened women were in a significantly higher socio-economic stratum than the women in the control group. The researchers conclude that only two studies, the Canadian Mammography Screening Study and a study carried out in Malmo, Sweden were sufficiently unbiased to be of value. The pooled results of these studies showed no reduction in breast cancer mortality due to the use of mammography screening. The researchers back up their contention that mammography screening is unjustified by pointing out that there has been no decrease in breast cancer mortality in Sweden since the introduction of mammography in 1985.
The researchers conducted a more detailed analysis of the findings from the Malmo and
Stockholm trials and found that women in the mammography groups were far more likely
to have undergone surgery and radiotherapy than had women in the control groups.
Dr. Harry J. de Koning of the National Evaluation Team for breast cancer screening in the
Netherlands comments on the Danish report in an accompanying editorial. He believes
there has been a reduction in breast cancer mortality in the UK due, in part, to the national
breast screening program. About 800,000 women are screened every year in the
Netherlands, but no statistically significant reduction in breast cancer mortality has been
found in the first nine years of the screening program. Dr. de Koning concludes that we
still need answers to the question "Are screening programmes justified and at what cost to
women and to society?"