Overview of screening risks

Breast cancer screening is not a harmless procedure. It exposes to 3 risks :
- a risk of overdiagnosis and overtreatment
- a risk of false alarms
- a risk of radiation-induced cancers

Overdiagnosis and overtreatment

Overdiagnosis is a malignant breast tumor discovered during screening that would never have harmed the woman's health if it had remained undetected.

The existence of overdiagnosis is no longer disputed by anyone. What is problematic, however, is the estimation of the importance of the phenomenon. Depending on the study, overdiagnosis may represent less than 10% to more than 40% of all cancers discovered by screening.
As can be seen, the range is quite broad. And it's not surprising: because we can't tell the difference between overdiagnosis and progressive cancer, we have to rely on complex statistical models to estimate the frequency of overdiagnosis. And each published study, or nearly so, employs its own model, which is neither more correct nor more false than the others, but yields different results.

The consequences of overdiagnosis are serious. Il faut bien comprendre que les surdiagnostics se présentent exactement comme les autres cancers. It is critical to understand that overdiagnosis is the same as other types of cancer. When confronted with a malignant tumor discovered during a screening, it is currently impossible to determine whether it is a cancer that will progress and cause health problems or an overdiagnosis.
Because it is impossible to distinguish between overdiagnosis and progressive cancer, all detected malignant tumors are treated as if they were progressive cancer. Overdiagnosis, as a result, leads to unnecessary treatment, or overtreatment. And it is not because overtreatment is unnecessary that it is less painful or causes fewer side effects, some of which are serious or even fatal.

More about overdiagnosis

False alarms

False alarms, also known as false positives, are caused by screening mammograms that raise the suspicion of breast cancer but are not confirmed by further testing.

The frequency of these false alarms is known. It is estimated that 80 false alarms occur for every 1000 screening mammograms (source InVS: Evaluation of the breast cancer screening program).
The consequences are obvious: unnecessary anxiety, unnecessary confirmation tests (including a number of biopsies).

Radiation-induced cancers

Radiation-induced cancers are cancers caused by X-rays used in mammogram screening.

According to the INCa (National Cancer Institute in France), the incidence of radiation-induced cancers ranges between 1 and 20 cases per 100,000 women who have been screened since the age of 50. (screening mammograms every 2 years from 50 to 74 years).

To summarize :
- breast cancer screening is far from a harmless act
- the main risk is over-diagnosis and unnecessary treatment. The consequences of over-diagnosis and over-treatment are significant, and they have an impact on the lives of the women who are victims. Unfortunately, the frequency of overdiagnosis and overtreatment remains little known and is the subject of debate
- false alarms are frequent but their consequences are limited
- repeated screening mammograms can cause cancers but the risk seems low.

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Dernière mise à jour le 12/09/2021