Fapesp: greater access to exams increases the incidence of thyroid cancer in rich regions

The incidence of thyroid cancer in the state of São Paulo varies considerably according to the socioeconomic level of patients and accessibility to preventive exams. However, mortality rates are similar among different populations. This is what a study published in the journal Endocrine Practice by researchers linked to the Hospital de Amor (formerly the Barretos Cancer Hospital) and the International Cancer Research Agency (Iarc). According to the authors, this result suggests the possibility of excessive diagnoses in areas with greater purchasing power.

Thyroid cancer is the most common malignant endocrine disease in the world, with a higher incidence among women (accounting for one in every 20 cancer diagnoses). In 2020, there were almost 600,000 new cases and more than 40,000 deaths, according to Iarc, an agency linked to the World Health Organization (WHO). Although it is more common in richer countries, it is also increasing in economies in transition, such as Colombia, Costa Rica, Ecuador and Brazil, a fact attributed by scientists to the more frequent performance of routine exams and the better detection potential of these tests.

In Brazil, thyroid cancer ranks seventh among the most common types of cancer and the number of thyroid ultrasounds and nodule biopsies has increased rapidly in the public health system in recent years.

Researchers from Hospital de Amor and Iarc investigated the geographic and socioeconomic occurrence of cancer in the 18 municipalities in the Barretos region, in the interior of São Paulo, between 2003 and 2017 and compared the data obtained with information relating to the capital of São Paulo (2001 -2015), where there is high accessibility to thyroid function tests, ultrasounds, MRIs and CT scans, among other exams. In the case of thyroid cancer, the discrepancy between the two regions was especially striking: the incidence observed in the city of São Paulo was three times higher (5.7 in the Barretos region and 15.9 in São Paulo, per 100 thousand people/ year).

For comparison purposes, according to the National Cancer Institute (Inca), throughout Brazil, the incidence of thyroid cancer is 4.8 and, worldwide, this number is 6.6, according to Global Scan ObservatoryIARC’s cancer statistics platform.

Furthermore, while in the Barretos region there was no significant variation in incidence between patients of different socioeconomic levels, which indicates uniformity in diagnostic practices, in São Paulo, the higher the social class, the more cancers of this type were detected (31 .6 in regions with the highest socioeconomic level versus 8.1 in the lowest).

Psychological impact

The study, which was supported by Fapesp through two projects (17/03787-2 and 21/10806-9), also showed that mortality rates were low in relative terms, both in the Barretos region and in the capital – in The most developed area analyzed was 0.3 and, in the least, 0.4 – leading researchers to believe that excess diagnoses is potentially responsible for the difference in incidences.

“When we talk about overdiagnosis, we are referring to tumors that, if not detected, would not result in symptoms or deaths – the person could even live for more than 90 years without any manifestation and would not die from this cause”, explains Adeylson Guimarães Ribeiro, currently deputy director of Information and Epidemiology at the Oncocentro de São Paulo Foundation (Fosp) and first author of the study. “However, once tests are carried out and a diagnosis is reached, a treatment protocol is initiated, generating physical and psychological impact.”

By contributing to a better understanding of the strong link between socioeconomic level, risk of diagnosis and death, the authors state, the results of the work suggest that a review of routine and diagnostic exam practices and policies is welcome, even to reduce unnecessary procedures and unwanted effects on patients’ lives.

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