So breast cancer screening really isn’t worth it – but women aren’t told that.

Supports Chapter 2: What’s behind the screens?

There is another gem in the British Medical Journal.

Peter Gøtzsche and colleagues argue that women are still not given enough, nor correct, information about the harms of screening.

Three years ago, Peter Gøtzsche and colleagues at the Nordic Cochrane Centre, the Department of Nuclear Medicine, and the University of Copenhagen, Denmark, published a survey of the information given to women invited for breast screening with mammography in six countries with publicly funded screening programmes. The major harm of screening, which is overdiagnosis and subsequent overtreatment of healthy women, was not mentioned in any of them.

This latest analysis shows that nothing has changed. Although the information that women were given should have been about both the benefits and adverse effects of breast cancer screening, the supposed benefits were hyped up, but the harms were still not mentioned. The authors say:

“By contrast, little information is given about harms. It states that "some women" find mammography uncomfortable or painful, which becomes "many women" in the summary. The summary also notes that recalls for more investigations "can cause worry." No mention is made of the major harm of screening - that is, unnecessary treatment of harmless lesions that would not have been identified without screening. This harm is well known and acknowledged, even among screening enthusiasts. It is in violation of guidelines and laws for informed consent not to mention this common harm, especially when screening is aimed at healthy people. The new guidelines from the General Medical Council state: "You must tell patients if an investigation or treatment might result in a serious adverse outcome, even if the likelihood is very small." The likelihood of being overdiagnosed after mammography is not very small; it is ten times larger than the likelihood of avoiding death from breast cancer.”

“Another harm is false positive diagnoses. The leaflet notes that about one in every 20 women screened will be recalled for more tests, but does not explain that this 5% rate applies to only one round of screening. The rate of false positive diagnosis after 10 screenings was 50% in the United States and 20% in Norway.”

And there are many more examples of the harm that mammography causes that are mentioned in Chapter 2 of Trick and Treat.

Gøtzsche and co publish a specimen leaflet which does list both sides. It is this:

Summary from evidence based leaflet
• It may be reasonable to attend for breast cancer screening with mammography, but it may also be reasonable not to attend because screening has both benefits and harms

• If 2000 women are screened regularly for 10 years, one will benefit from the screening, as she will avoid dying from breast cancer

• At the same time, 10 healthy women will, as a consequence, become cancer patients and will be treated unnecessarily. These women will have either a part of their breast or the whole breast removed, and they will often receive radiotherapy and sometimes chemotherapy

• Furthermore, about 200 healthy women will experience a false alarm. The psychological strain until one knows whether it was cancer, and even afterwards, can be severe

But I doubt that women will be told the truth. If they were, they would probably say ‘no, thank you’ and doctors would then see a cut in their salaries – and that would never do, would it?

Gøtzsche PC, et al. Breast screening: the facts—or maybe not. BMJ 2009;338:b86
doi:10.1136/bmj.b86