According to the researchers, the positive impact of screening is gradually falling as cancer treatment improves.
A recent study raises the issue of whether the advantages of breast cancer screenings have steadily diminished to the point where they are no longer outweighed by the costs associated with overdiagnosis and overtreatment.
Breast cancer screening is costly. This is shown by a Danish/Norwegian study that examined 10,580 breast cancer fatalities among Norwegian women between the ages of 50 and 75.
“The beneficial effect of screening is currently declining because the treatment of cancer is improving. Over the last 25 years, the mortality rate for breast cancer has been virtually halved,” says Henrik Støvring, who is behind the study.
The issue, according to the researchers, is that screenings result in both overdiagnosis and overtreatment, which has a cost on both a human and economic level.
Overdiagnosis and overtreatment
When screening was first implemented, it was estimated that around 20% of breast cancer-related deaths among those screened may be avoided. This equated to around 220 deaths a year in Denmark 25 years ago, but the figure has now been cut in half.
According to the study, whereas it took 731 women to prevent one breast cancer death in Norway in 1996, it would take at least 1364 and likely closer to 3500 women to accomplish the same result in 2016.
The negative consequences of screening, however, remain the same.
“One in five women aged 50-70, who is told they have breast cancer, has received a ‘superfluous’ diagnosis because of screening – without screening, they would never have noticed or felt that they had breast cancer during their lifetime,” says the researcher.
One in five corresponds to 900 women annually in Denmark. In addition, every year more than 5000 women are told that the screening has given rise to suspicion of breast cancer – a suspicion that later turns out to be incorrect.
Peaceful, small nodes – but in who?
Henrik Støvring notes that the result is not beneficial for the screening programs. According to him, the Norwegian results can also be transferred to Denmark. Here, women between 50 and 69 are offered a mammogram screening every second year. This is an X-ray examination of the breast, which can show whether the woman has cellular changes that could be breast cancer.
The Danish screening program became a national program offered to all women in the age group in 2007 – three years after the Norwegians. Approx. 300,000 Danish women are invited to screening for breast cancer every year.
According to the researcher, the challenge is that we are not currently able to tell the difference between the small cancer tumors that will kill you and those that will not. Some of these small nodes are so peaceful or slow-growing that the woman would die a natural death with undetected breast cancer if she had not been screened. But once a cancer node has been discovered, it must of course be treated, even though this was not necessary for some of the women.
“The women who are invited to screening live longer because all breast cancer patients live longer, and because we have got better drugs, more effective chemotherapy, and because we now have cancer care pathways, which mean the healthcare system reacts faster than it did a decade ago,” says Henrik Støvring.
Reference: “Change in effectiveness of mammography screening with decreasing breast cancer mortality: a population-based study” by Søren R Christiansen, Philippe Autier and Henrik Støvring, 23 June 2022, The European Journal of Public Health.
DOI: 10.1093/eurpub/ckac047
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