Most thyroid cancers still detected in asymptomatic patients
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In an international cohort of adults undergoing thyroid cancer surgery, most cancers were discovered among those with no thyroid-referable symptoms and 34% were symptomatic, according to study data.
“Most thyroid cancers continue to be discovered in asymptomatic patients, supporting the hypothesis of ongoing detection of subclinical disease rather than a true increase in disease,” Mirabelle Sajisevi, MD, an otolaryngologist at the University of Vermont (UVM) Medical Center and assistant professor at the Larner College of Medicine at UVM in Burlington, and colleagues wrote.
The researchers conducted a retrospective analysis using pathology and medical records of 1,328 adults (mean age, 52 years; 75% women) who received thyroid-directed surgery at 16 centers in Canada, Denmark, South Africa and the United States. They included the first 100 patients — or the largest number available — at each center who underwent thyroid surgery in 2019.
According to data, 34% of surgeries were for patients with thyroid-related symptoms, whereas 41% were for thyroid findings discovered without thyroid-referable symptoms, 14% for endocrine conditions and 12% for nodules under surveillance with original mode of detection unknown.
In all, cancer was detected in 46% of patients, of whom 30% were symptomatic and 51% had no thyroid-referable symptoms. In the symptomatic group, mean size of the identified cancers was 3.2 cm (95% CI, 2.91-3.52), whereas in the asymptomatic group mean nodule size was 2.1 cm (95% CI, 1.92-2.23).
Furthermore, there were significant pattern differences in mode of detection between the participating countries.
“In the future,” the researchers concluded, “focused examination of the mode of detection for people who present with advanced disease at diagnosis to determine whether these cancers are found incidentally or because of symptoms may lend additional insights that could help with continued efforts to parse the potentially evolving epidemiology of the disease and test the hypothesis of a true increase in the incidence of thyroid cancer.”
In an accompanying commentary, Tyler Drake, MD, and Emiro Caicedo-Granados, MD, both of the Minneapolis Veterans Affairs Health Care System, wrote that the study confirms that many patients who undergo thyroid surgery initially present as asymptomatic.
“Despite a lack of symptoms, patients are found to have thyroid pathology, most often thyroid nodules, which begins a process that often ends with surgery and the diagnosis thyroid cancer,” Drake and Caicedo-Granados wrote. “This aggressive evaluation and treatment cascade of asymptomatic patients is likely contributing to the overdiagnosis and overtreatment of thyroid cancer. Future efforts are required to shift toward a less aggressive process, including preventing inappropriate evaluation with screening thyroid ultrasonography and increased implementation of active surveillance protocols of small papillary thyroid carcinomas, to avoid unnecessary and inappropriate thyroid surgery.”
Perspective
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From the 1980s to mid-2010s, thyroid cancer incidence increased rapidly in the United States, and this increase was steepest for small papillary thyroid cancers localized to the thyroid gland. These trends appear to have been driven largely by overdiagnosis, resulting from an improved ability to detect and diagnose small or indolent thyroid cancers through the more widespread and growing use of diagnostic ultrasounds and imaging tests performed for unrelated reasons. More and more individuals were unnecessarily labeled as cancer patients and underwent treatments for a disease that would never have caused them any harm if left undetected. In the last 10 to 15 years, clinical practice guidelines evolved substantially, shifting toward a more cautious, risk-stratified approach to thyroid cancer diagnosis and management. As a result, the incidence of thyroid cancer began to decline for the first time in decades. In addition, more patients underwent lobectomy, instead of total thyroidectomy, and fewer received radioactive iodine treatment.
The current study identified the initial mode of detection for 702 benign/in situ and 613 malignant nodules that were surgically removed in 2019 across four countries (Canada, Denmark, South Africa and the United States). Only 30% of the cancers and 37% of benign nodules were symptomatic at presentation. The most common reasons for discovery of asymptomatic thyroid cancers were routine clinical screening examination and radiologic imaging done for unrelated reasons, such as computed tomography, positron emission tomography or magnetic resonance imaging of the head, neck or chest. Asymptomatic thyroid cancers were generally smaller than symptomatic thyroid cancers, although a small number were larger than 4 cm. As smaller tumor size is associated with less-aggressive disease, this finding demonstrates that overdiagnosis of thyroid cancer continues to be an important and common clinical and public health issue. It will be important to continue monitoring these mode of detection patterns over time to determine whether additional efforts are needed to combat thyroid cancer overdiagnosis.
In practice, it is not clear whether, and to what extent, mode of detection is routinely recorded in patient records or influences diagnostic follow-up and treatment decisions. Additional research may be needed to determine whether mode of detection predicts patient outcomes independently of tumor stage, size and other clinical and pathological indicators of disease aggressiveness. If so, incorporation of mode of detection in clinical decision-making may help to more accurately identify patients who are more or less likely to benefit from diagnostic follow-up and more extensive therapeutic strategies.
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