in many developed countries, including the Unites States, concluded a new analysis based on 30 years of observational data.
“We report overall increases in the burden of thyroid cancer across the majority of EU15+ countries between 1990 and 2019, evidenced by plateaus in incidence rates and reductions in mortality and DALY [disability-adjusted life-years] rates,” the authors reported.
“However, in a number of countries, including the U.S., there are unfavorable increasing mortality and DALY trends over this time period ... [and] a better understanding of the trends in the disease burden of thyroid cancer may help to inform future health system planning,” they added.
The study was published online March 10, 2022, in JAMA Otolaryngology–Head & Neck Surgery.
Trends in thyroid cancer
For the analysis, James Schuster-Bruce, MBChB, from St. George’s University Hospital NHS Foundation Trust, London, and colleagues compared trends in thyroid cancer across 30 years of follow-up among 15 countries of the (pre-2004) European Union as well as those in the United States, Australia, Canada, and Norway (EU15+).
Data from the Global Burden of Disease study database were used to track these trends. “We extracted age-standardized incidence rates (ASIRs), age-standardized mortality rates (ASMRs), and DALYs for thyroid cancer from EU15+ countries between 1990 and 2019 using the dedicated GBD study results tool,” the investigators explained.
In 2019, ASIRs were highest in Italy at 6.36 per 100,000 population, followed by the United States at a rate of 5.59 per 100,000 population – although incidence rates of thyroid cancer have actually recently decreased in U.S. women, they noted.
“Thirteen of 19 countries showed an average annual percentage increase in ASIR across the study period,” the investigators added. Out of all the EU15+ countries, the average annual percentage change (AAPC) was the highest in Australia at 2.5 per 100,000 population and the United States at 1.2 per 100,000.
On the other hand, a largely plateauing trend in incidence rates across the majority of EU15+ nations has been observed since 1990, as reflected by incidence rates ranging from –0.8 to 0.8 per 100,000 in the most recent period, the researchers added. ASMRs ranged from a 0.40 per 100,000 in Greece to 0.57 per 100,000 in Luxembourg.
In the United States, the ASMR in 2019 was 0.43 per 100,000 population while the ASMR was the lowest in the United Kingdom in the same year at 0.38 per 100,000 population.
Australia, Denmark, and the United States were the only countries showing positive AAPC changes, the team observed. For example, in the most recent period to 2019, Denmark and Australia had reductions in ASMR trends, whereas in the United States, the trend was toward increasing ASMRs
In 2019, the DALYs of the EU15+ nations ranged from 9.63 per 100,000 in the United Kingdom to 14.46 per 100,000 in Luxembourg. In the most recent period, a downward trend in DALYs was observed in Australia and Denmark while it plateaued in the United States.
“Overall, we identified improvements in thyroid cancer mortality and DALYs, but overall increases in thyroid cancer incidence in EU15+ countries over the past 3 decades,” the investigators commented.
It has been widely suggested that improvements in diagnostic techniques have contributed significantly to increasing incidence rates of thyroid cancer, but there is concern about overdiagnosis. Newer diagnostic techniques detect significant numbers of slow-growing, subclinical papillary thyroid cancers that make up at least one quarter of all thyroid cancer subtypes, the authors pointed out.
“It has therefore been suggested that an increase in subclinical disease has inflated the data to look more substantial than the clinical reality,” the authors wrote. However, they insisted that overdiagnosis alone is unlikely to account entirely for increasing incidence trends in the current analysis.
Rather, their concern for countries with high incidence rates of thyroid cancer is the surveillance burden of disease that does not affect mortality. “Close observation of future time trends in thyroid cancer disease burden should be performed in the context of recent changes in international clinical practice guidelines, which have suggested more conservative diagnostic and management strategies,” the authors suggested.
“In the context of the more conservative treatment guidelines and reported increase in true disease, it is important to closely observe mortality and DALYs over the coming years to ensure optimum thyroid cancer management in these nations,” they added.
The study had no specific funding. Dr. Schuster-Bruce disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.