June 5, 2020
Summary, Cécile Bour, MD
IARC concerned about overdiagnosis of thyroid cancer
Overdiagnosis is a real problem in our over-medicalized modern societies. It is becoming a vast public health issue, leading entire populations into the torments of disease that they would not have experienced without the unnecessary over-detection by all kinds of screening, of which so-called "preventive" medicine is so fond.
The physician and methodologist D. Sackett is very critical of preventive medicine, which he describes as follows:
- Affirmative on healthy individuals without any symptoms, telling them what to do to stay healthy;
- Presumptuous, claiming that its interventions will generally do better rather than worse to those who adhere;
- Tyrannical, doing everything possible to exert its authority through media campaigns based on public fears, and attacking its opponents.
Concerning thyroid cancer screening, which we will discuss below, the female population is once again paying the price of unrestrained over-medicalization, as for breast cancer.
Overdiagnosis of cancers
Overdiagnosis is the undesirable surprise-guest of mass population screening. Dr. B. Duperray has contributed enormously to a better knowledge of overdiagnosis in breast cancer screening.
Screening for prostate cancer, which is still prescribed, is no longer recommended by the health authorities because of serious damage to men's health. In an article of 2017, we discussed its overdiagnosis.
Things seem more nuanced for colon cancer screening, with a screening whose logic of promotion is moving from a screening for all , rather to a proposal for patients most at risk (with risk of colorectal cancer at 15 years ≥3%), this done with a fair information of the patient and a shared decision.
(Colorectal cancer screening with faecal testing, sigmoidoscopy or colonoscopy: a systematic review and network meta- analysis
Henriette C Jodal, Lise M Helsingen , Joseph C Anderson, Lyubov Lytvyn, Per Olav Vandvik, Louise Emilsson Jodal HC, et al. BMJ Open 2019;9:e032773. doi:10.1136/bmjopen-2019-032773)
Overdiagnosis of thyroid cancer
Overdiagnosis of thyroid cancer is a well-known phenomenon, already mentioned as early as 2016  by the IARC  itself .
In a 2016 NEJM study, it was estimated that more than half a million patients were over-diagnosed between 1988 and 2007 in 12 high-income countries, with a dominant female population.
At the time, the IARC was already denouncing the high rise in the number of small papillary thyroid cancers (the most frequent and least dangerous form) and that, since 80-90s.
According to researchers, this alarming increase in the number of small papillary cancers, observed in France and in several developed countries (United States, South Korea, Italy, Japan), is above all the consequence of the growing use of increasingly precise imaging methods, in particular cervical ultrasound, and not the consequence of other factors sometimes cited such as the impact of nuclear accidents. According to researchers, up to 90% of thyroid cancers diagnosed in recent decades, mostly in women (84% in France), are most often overdiagnosed.
New IARC alert
"Overdiagnosis of thyroid cancer is increasing rapidly around the world and has become a major public health challenge," warn researchers at the International Agency for Research on Cancer once again.
In collaboration with the Aviano National Cancer Institute in Italy, cancer registries in 26 countries on four continents were studied. Recently published in "The Lancet Diabetes & Endocrinology", the study found a very significant increase in thyroid cancer incidence (rate of new cases) between the periods 1998-2002 and 2008-2012 in all analyzed countries.
This overdiagnosis of thyroid cancer is more pronounced in middle-aged women (between 35 and 64 years old). The proportion of overdiagnosis from 2008-2012 varied around 40% in Thailand and over 90% in South Korea.
In France, the overdiagnosis rate among women is estimated by the authors at 83%, which corresponds in gross figures to 25,000 patients between 2008 and 2012.
In all countries
More than 830,000 women and over 220,000 men may have been overdiagnosed between 2008 and 2012.
The origin of the problem
The origin of the problem should be sought in medicine itself, the authors point to the increased surveillance of the thyroid gland, in particular by cervical ultrasound, leading to the over-detection of many harmless tumors, that will be all treated once found.
In South Korea, where the phenomenon was well monitored, overdiagnosis was the consequence of the thyroid examination routinely performed in screening programs.
IARC researchers urge governments to be vigilant and to review recommendations for screening asymptomatic patients.
Overdiagnosis leads to lifelong damage, overdiagnosed lesions are all treated with radical thyroid ablation and replacement therapy for the rest of the patient's life. The psychological consequences of the announcement of cancer are often dramatic and should not be underestimated.
A financial consideration is not insignificant: the costs generated by over-diagnosis divert countries' resources to other areas of care more appropriate to the health of the population.
This problem is very well addressed by the science journalist John Horgan, in an article on what he names "the cancer industry", which we have shared.
2] WHO International Agency for Research on Cancer, based in Lyon.