Breast cancer is routinely overdiagnosed in Norway
For every life saved from breast cancer by the Breast Cancer Screening Programme, five women are over-diagnosed, and have to go through an operation to remove a tumour that otherwise never would have caused problems.
MAMMOGRAMS AND BREAST CANCER: This is one of several conclusions to an evaluation of the Breast Cancer Screening Programme done by several Scandinavian researchers.
The Norwegian government spends NOK 574 million per screening round to check women between the age of 50 and 69 for breast cancer. An ongoing debate between Norwegian and international researchers and doctors considers the wisdom of offering periodic breast cancer screenings.
On task from the Ministry of Health and Care Services, the Research Council of Norway has done a research-based evaluation of the country’s Breast Cancer Screening Programme.
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Disparity in research results
The evaluation was led by Professor Roar Johnsen at NTNU. Together with postdoctoral fellow Signe Opdahl and the rest of the steering committee, they have gone through all studies done on mammograms in Norway since 2008.
The conclusions of these studies, however, are inconsistent. One report shows that mammograms have reduced the amount of cancer deaths by 10 per cent, while another claims as much as 36 per cent. The evaluation that is now being presented is based on all of these different studies.
Uncertainty in the numbers
Here are a few of the conclusions in the evaluation:
– Breast cancer deaths have been reduced in Norway by roughly 20 to 30 per cent as a result of the screening programme.
– The screening results in overdiagnosis of 15-20 per cent.
– For every 27 women who avoid dying of breast cancer, 142 women are overdiagnosed and treated unnecessarily.
– There are a lot of uncertainties in these numbers, because the studies that the evaluation looked at are all very different, and because factors such as the use of mammograms at private clinics and hormone treatment during menopause are things that most studies have not been able to consider.
– From a social perspective, the balance between cost and effect is within the level that health authorities consider to be acceptable for health care services.
Achieving the goal of the Breast Cancer Screening Programme
“The goal of the Breast Cancer Screening Programme was to reduce breast cancer mortality rates by 30 per cent. Depending on how you look at it, our estimates show that this goal may have been reached. But it has taken a huge toll in the form of overdiagnosis,” says Johnsen.
In 2013, Swiss authorities were advised to end their breast cancer screening programme, while England was advised to continue theirs in 2012. Most Western countries have some kind of screening programme available.
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Up to each individual to decide
“One challenge we face is that if a small tumour that is most likely benign is discovered, we can’t take the chance of not treating it. This means that women have to go through cancer treatment, with all of the social and personal costs it brings unnecessarily. More money should be given to research so that we have more knowledge about which tumours do and do not need treatment. Each individual woman needs to consider the pros and cons from her side when she decides if she wants to participate in the Breast Cancer Screening Programme,” says Johnsen.
About three quarters of women between 50 and 69 years of age choose to participate in screening.
The evaluation was given to Minister of Health and Care Services Bent Høie on 5 June.
“We have now presented the basis for a political decision,” Johnsen concludes.
