« Is breast cancer screening useless or even harmful ? » : analysis of French National Cancer Institute (INCa) arguments

After a post denouncing the unacceptable conduct of INCa, which treats as Fake news any questioning on the interest of breast cancer screening, here is an analysis of the arguments used by INCa. ( Access to the INCa website)

Let’s begin with a consensual point: it is undeniable that an early malignant tumor is easier to treat and has a better prognosis than a very advanced malignant tumor.
No one disputes this fact. What is disputed by some, is whether screening can detect advanced tumors at an early stage.

INCa acknowledges the reality of overdiagnosis but presents as evidence a frequency of 10 to 20% of malignant tumors detected during screening.
In reality, this figure of 10 to 20% is neither "true" nor "false". In the scientific literature, depending on the study, the frequency of overdiagnosis varies from a few percent to nearly 50%. The figure of 10 to 20% has no scientific basis but is only an opinion, an "average" estimate, of the experts from INCa.
In the scientific uncertainty of the true frequency of overdiagnosis, this estimate is worth another, but it is dishonest to present it as an established fact.

INCa's arguments strongly emphasize the value of early diagnosis and a reduction in breast cancer mortality, claimed to be between 15 and 21%.
On the other hand, the absence of a reduction in overall mortality is not mentioned. However, this is the main point of interest for a woman who is wondering whether or not she should participate in screening.

The risks of screening are presented in a caricatured way. The argument largely insists on minimizing the risk of radiation-induced cancers.
Overdiagnosis and overtreatment, which are the main risks of screening, are hardly mentioned. Moreover, when they are mentioned, it is mainly to remind the public that these are "real" cancers.

With such an imbalance in the presentation of benefits and risks, it is not surprising that INCa categorically concludes, « Le dépistage des cancers du sein apporte aux femmes un bénéfice bien plus important que ses risques. » (Breast cancer screening brings women a far greater benefit than its risks.)
This statement is presented by INCa as indisputable evidence. And it neglects physical, psychological and social suffering that will be caused by the overdiagnosis and overtreatment resulting from screening.

The reality of the benefit/risk ratio of screening is :

• on the one hand, for women who refuse screening, the risk of dying from breast cancer that could have been cured earlier when diagnosed by a screening mammogram,
• on the other hand, for women who participate in screening, the risk of overdiagnosis, with all the physical, psychological and social consequences of overdiagnosis and overtreatment.

Clearly, the INCa has chosen to consider overdiagnosis and overtreatment as the price to be paid to avoid breast cancer deaths. This is a logical choice.
But it is not the only choice. Considering that overdiagnosis and overtreatment are an excessive price to pay to avoid a few deaths from breast cancer, without any significant improvement in life expectancy, is a choice that also has its logic and is entirely respectable.

What is certain, and it doesn't matter whether INCa considers it as fake news, is that both options can be defended.
And it is up to each woman, and only to her, to make her choice, after having been honestly and completely informed.

---

Dernière mise à jour le 12/09/2021