The incidence of thyroid cancer in adolescents and young adults has dramatically increased over the last two decades but mortality rates remain stable.
Experts have called for reduced thyroid screening in adolescents and young adults after a new study showed rapidly increasing thyroid cancer rates without rising mortality.
The number of adolescents and young adults (AYAs) with cancer has dramatically increased in recent decades, with thyroid cancer being a key contributor to this change. Now, a new international study has evaluated trends and explored the current burden of thyroid cancer in AYAs on a global scale.
“Given the distinctive nature of thyroid cancer in AYAs, the rapidly evolving landscape, and the knowledge gaps in the effect of overdiagnosis on its global epidemiology, up-to-date analyses focusing on this population are crucial,” the researchers wrote in The Lancet Diabetes & Endocrinology.
Using data from the Cancer Incidence in Five Continents Plus and World Health Organization databases, an international team of researchers examined temporal trends in the incidence and mortality rates of thyroid cancer over a 15-year period.
There were trends of increasing incidence for almost all 185 included countries. Data from 2022 indicated that the age-standardised rate of thyroid cancer incidence was 11.0 per 100,000 females and 3.8 per 100,000 males. South Korea, China and Ecuador were among the countries with the largest increases in incidence rates this millennium.
The average incidence-to-mortality ratio for thyroid cancer in AYAs was 122 for females and 95 for males. To put these results in context, many other common cancers have ratios below 10.
While Australian data were included in the study, the exact changes in incidence and mortality rates were not specified. An unlabelled graph suggests the average annual percent change for thyroid cancer incidence between 2003 and 2017 sat at approximately 3% for females and close to 5% for males.
A more detailed account of local thyroid cancer data can be found in the Cancer data in Australia report, released by the Australian Institute of Health and Welfare in late 2025. The document also reports that the incidence of thyroid cancer is trending upwards.
“The incidence of thyroid cancer increased from 8.5 cases per 100,000 females in 2000 to an estimated 21 cases in 2025. While lower, the incidence rates for males have also increased from 3.3 cases to an estimated 10.0 cases per 100,000 males over the same period,” the report reads.
“[But] despite an increase in the incidence rate, the mortality rate for thyroid cancer has been broadly stable since 2000, between 0.5 and 0.7 cases per 100,000 people.”
The Cancer data in Australia report uses different age categories for AYAs compared to The Lancet Diabetes & Endocrinology study, but the best comparators show similar trends. Between 2003 and 2017 the age-specific rate of thyroid cancer increased from 9.1/100,000 people to 13.6/100,000 among 15-24-year-olds and from 37.9/100,000 to 52.5/100,000 over the same period in 25–34-year-olds.
Both the new study and the AIHW report agree on the main driver for the increase in thyroid cancer incidence: overdiagnosis.
“The last 3–4 decades have seen a growing, opportunistic use of diagnostic imaging in AYAs, driven by greater access to low-cost medical facilities (e.g., ultrasound), the use of imaging for unrelated clinical reasons (e.g., X-rays for trauma, dental or occupational checkups) and scrutiny of the thyroid gland due to gynaecological and obstetric concerns,” the researchers wrote.
“This expanding diagnostic surveillance has likely contributed to the detection of a large reservoir of subclinical thyroid nodules, many of which would not have caused symptoms or clinical concern in the absence of imaging.
“Moreover, when treating younger patients, clinicians might adopt a more aggressive diagnostic and therapeutic approach, favouring early biopsy or surgery even for small or indolent lesions, further enhancing the effects of overdiagnosis and overtreatment.”
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The authors of an accompanying commentary elaborated on the potential risks associated with overdiagnosis.
“Mortality from thyroid cancer in AYAs is low and remained stable or slightly decreased during the last three decades despite the large increase in incidence. The consequences of this overdiagnosis are even more severe among AYAs than in older populations,” they wrote.
“Beyond the physical harms – including rare complications from surgery and radioactive iodine treatment, lifelong thyroid hormone replacement therapy and avoidable financial costs for both patients and healthcare systems – AYAs face unique challenges. Being labelled as having cancer early in life results in worse physical, psychosocial, and financial effects than when the diagnosis occurs at older age.
“Accordingly, routine screening for thyroid cancer in asymptomatic AYAs without risk factors is strongly discouraged.”
