Ineffective and harmful medical practices have always been with us, but the scale and institutionalisation of overdiagnosis and overtreatment have expanded exponentially in the last few decades, fueling a reasonable doubt ” Too much medicine? “.
Overdiagnosis has been defined simply as ‘… when people without symptoms are diagnosed with a disease that ultimately will not cause them symptoms or early death’.
Overdiagnosis is a relatively new problem in medicine. In the past people did not go to the doctor when they were well. The tended to wait until they developed symptoms. Furthermore, in the past, doctors did not encourage the symptomless individuals to seek care. The net result was that doctors made fewer diagnosis than they do now.
Drivers of overdiagnosis are many.
– Advancing technology: allowing detection of disease at earlier stages or ‘pre-disease’ state
– genuine and well-intentioned enthusiasm: most of the people (including policy makers, politicians, doctors) sincerely believe that making more diagnoses is the path for better health. They take for grant the intuitive thinking – yet not supported by data – that early diagnosis improves the outcomes. It’s spontaneous and intuitive to think in this direction.
– vested interest: Pharmaceutical Industry, sponsored researches, etc.
– medico-legal fear (doctors tend to be sued for under-diagnosis rather than for over-diagnosis)
– payment and performance indicators that reward over-activity
– built-in predilection for certainty and fear of uncertainty
Let’s consider, in this section, overdiagnosis in relation to the thyroid cancer (i.e. the diagnosis of tumors that are very unlikely to cause symptoms or death during a person’s lifetime).
The International Agency for Research on Cancer (IARC) – in collaboration with the Aviano National Cancer Institute in Italy – has shown that the growing epidemic of thyroid cancer reported in recent decades in several high-income countries is largely due to overdiagnosis. IARC has published the results in The New England Journal of Medicine in 2016. They reports that countries such as the USA, Italy, and France have been most severely affected by overdiagnosis of thyroid cancer since the 1980s, after the introduction of ultrasonography, but the most recent and striking example is the Republic of Korea. A few years after ultrasonography of the thyroid gland started being widely offered in the framework of a population-based multi-cancer screening, thyroid cancer has become the most commonly diagnosed cancer in women in the Republic of Korea, with approximately 90% of cases in 2003–2007 estimated to be due to overdiagnosis.” The estimated fraction of overdiagnosed cases in women during the same period ranges between 70% and 80% in Australia, France, Italy, and the USA, while it is approximately 50% in Japan, the Nordic countries, and England and Scotland. The proportion of cases of thyroid cancer in men that were estimated to be overdiagnoses is approximately 70% in France, Italy, and the Republic of Korea, 45% in Australia and the USA, and less than 25% in all other countries examined.
In total, IARC has estimated that more than 470 000 women and 90 000 men may have been overdiagnosed with thyroid cancer during two recent decades in the 12 countries studied.
The majority of the overdiagnosed thyroid cancer cases undergo total thyroidectomy and frequently other harmful treatments, like neck lymph node dissection and radiotherapy, without proven benefits in terms of improved survival,” says Dr Silvia Franceschi, one of the authors of the article.
In USA, many researchers stumbled into the same result. Between 1975 and 2009, the incidence of thyroid cancer, in america population, nearly tripled (from 4.9 per 100 000 to 14.3 per 100 000), whereas the death rate remained constant (from 0.56 per 100 000 to 0.52 per 100 000). The increase in incidence has been almost entirely due to small (<2 cm) papillary cancers, the most non-progressive histological type.
From the collected data, the Epidemic of thyroid cancer seems more an Epidemic of diagnosis.
An increase in incidence largely confined to the more indolent histological subtype and to early tumor stages, without concomitant increase in mortality, suggests cancer overdiagnosis, that is the detection of indolent cancer forms that will neither cause symptoms during a persons’ lifetime, nor reduce lifespan .
Jegerlehner S. and coworkers have showed the same large rise of incidence of thyroid cancer in Switzerland, confined to papillary carcinoma and early stage tumors, with a concomitant three- to four-fold increase in the rate of thyroidectomy and a slight decrease in thyroid cancer mortality in Switzerland between 1998 and 2012. These findings suggest that a substantial and growing part of the detected thyroid cancers are overdiagnosed and overtreated.
Due notably to the harms of overdiagnosis, the US Preventive Services Task Force has recently updated its recommendation against routine screening for thyroid cancer.
Harach and coworkers performed an autoptical study on Finnish women died for reasons differently from cancer. They found that 36% of participants, without any previous history of thyroid disease, had at least one papillary carcinoma at autopsy.
The rapid growth of ultrasound and fine-needle aspiration in the mid-1980s probably increased detection. Although only 4–7% of the adult US population has a palpable thyroid nodule, about 50% have a thyroid nodule detectable by ultrasound.
One thoughtful radiologist has questioned whether it is “time to turn off the ultrasound machines” because the impalpable cancers detected by ultrasound are almost uniformly indolent.
Because most thyroid cancers are primarily treated by surgery, i.e., partial or total thyroidectomy, overdiagnosis leads to overtreatment through the performance of unnecessary thyroidectomies without clear benefit for the patient.
Surgery — typically total thyroidectomy — carries a 1% – 2% chance of damaging the patient’s voice and a 1% – 2% chance of causing permanent hypoparathyroidism and requiring lifelong medication. One or two percent seems very low unless it happens to be you, in which case it’s 100%. That trade-off seems particularly high for a disease that probably will not ever harm the patient.
Being labeled as cancer patients, patients begin to behave and to think differently, which can precipitate a different set of negative consequences. The emotional burden “I have the cancer” can compromise heavily the quality of life, triggering anxiety, insecurity, panic, and other form of distress – often involving the rest of the family.
When you’re trying to find thyroid cancer, you have to balance not only the alleged benefits but also these unexpected consequences.
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