April 23, 2020
Randomized clinical trial by "cluster" (cluster)
Authors: Mara A. Schonberg, MD, MPH; Christine E. Kistler, MD, MASc; Adlin Pinheiro, MA et al.
A cluster randomization trial is a trial in which subjects are randomized not individually but by randomization unit or groups of subjects, known as "clusters".
Here 546 women aged 75 to 89 years, who received a decision aid on mammography screening prior to a health care visit with their practitioner, constitute the randomization unit.
Purpose of the study :
To investigate how the use of a screening decision aid for women 75 years of age and older affects their decision to participate in mammography screening.
Providing these women with a mammography screening decision aid prior to their medical visit helps them make informed decisions and leads to fewer women undergoing mammography screening.
Therefore a decision support tool can help reduce overscreening.
Cécile Bour, MD
Such a study could be of interest on younger age groups, although an assessment of what concerned women perceive and the impact of the lack of balanced information has already been carried out .
How do women perceive the benefits of screening according to what has been conveyed about it, and according to the information they have received, and which has forged their convictions on the subject?
This is the question posed in this study by Domenighetti et al, according to which the table below was drawn up by Nikola Biller-Andorno, a bio-ethics researcher who collaborated on the work of the Swiss Medical Board.  
In this comparative table we can find, in part A, data from Domineghetti's American Women's Perception Survey, and in part B, actual data from the most likely scenarios, found from the most convincing and reliable studies. 1-3)
The authors (Biller-Andorno et al.) were stunned by the significant discrepancy between women's beliefs about the benefits of screening and the reality, and legitimately asked the question: how could women make an informed decision if the benefits of the procedure were overestimated?
See our article with the detailed results of this work here: https://cancer-rose.fr/en/2020/12/18/perception-and-reality-2/
For the moment, the decision-making tool for women requested by the citizen consultation is completely absent in France, since 2016 when the consultation took place.
There is indeed a question of establishing one " in the French way ", which will hardly be possible given the deficient epidemiological data in our country .
Recently in JAMA a viewpoint was published on recommendations for shared decision making with the patient .
Unfortunately at the moment it seems that the shared decision is more a medical " dream " than a reality.
Indeed, recommendations from learned societies always have more weight than the values and experiences of the patient, and are sometimes imposed in the media and on patients with great virulence and authoritarianism, as we saw in 2019 with the abusive campaign of the French national college of obstetricians and gynecologists (CNGOF), advocating the extension of screening to the elderly, without any national or international recommendation. The Council of the Order, which we had alerted, did not react , even though it regularly calls to order those who violate the communication of verified medical notions, as is currently the case in the Covid context.
There is still an enormous amount of work to be done so that the values and reality of each patient's life, including her age, can guide the practice of every physician. There is also a long way to go, to ensure that physicians have the practical means to contribute to shared decision making, so that women, both older and younger age groups, finally have access to real tools made on a correct and independent scientific basis.
The development of such tools implies admitting the possibility of women's refusal to participate in screening, as the performance of mammography screening has proven over the decades and in the course of modern studies to be increasingly disappointing.
The real problem is that neither health authorities nor politicians are prepared to accept the possibility of women refusing to be screened for political and ideological reasons, thus depriving them until now of true autonomy in health.
 Domenighetti G, D'Avanzo B, Egger M, et al. Women's perception of the benefits of mammography screening: population-based survey in four countries. Int J Epidemiol2003;32:816-821 CrossRef | Web of Science | Medline
 1. Gotzsche PC, Jorgensen KJ. Screening for breast cancer with mammography. Cochrane Database Syst Rev 2013;6:CD001877-CD001877 Medline/
- Independent UK Panel on Breast Cancer ScreeningThe benefits and harms of breast cancer screening: an independent review. Lancet 2012;380:1778-1786 CrossRef | Web of Science | Medline/
- Miller AB, Wall C, Baines CJ, Sun P, To T, Narod SA. Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial. BMJ 2014;348:g366-g366 CrossRef | Web of Science | Medline/