Patterns of thyroid cancer still point to overdiagnosis


By Mardi Chapman

11 Feb 2022

Overdiagnosis of thyroid cancer has become a major public health issue in many settings, according to evidence from 185 countries including Australia.

The study, published in The Lancet Diabetes Endocrinology, said Australia had one of the highest age-standardised incidence rates for thyroid cancer in women but one of the lowest mortality rates.

It found global age-standardised incidence rates of thyroid cancer were about 10·1 per 100,000 women and 3·1 per 100,000 men. In both sexes, rates were five times greater in high and very high Human Development Index (HDI) countries than in low and medium HDI countries.

Mortality rates were about 0·5 per 100,000 women and 0·3 per 100,000 men for a global total of about 44,000 deaths in 2020. Europe, North America, Australia and New Zealand had the lowest mortality rates.

The discrepancy between high incidence and low mortality was strongly suggestive of overdiagnosis, the study said.

A Comment article in the journal said over diagnosis resulted in overtreatment which had no benefit in terms of cure and might be associated with a high financial burden.

“For all these reasons, overdiagnosis should be limited. Guidelines discourage the use of neck ultrasonography in asymptomatic patients without risk factors and suggest to submit suspicious nodules to a fine-needle biopsy for cytology only when their size is more than 1 cm in diameter.”

It said overtreatment should also be limited.

“In some patients with a papillary thyroid cancer of less than 1 cm in diameter, an active surveillance might be offered with surgery only at progression (increase in tumour size or appearance of suspicious lymph nodes) that will provide similar results as immediate surgery; in patients with low-risk thyroid cancer, a limited treatment might be proposed with lobectomy alone, when the cancer is unilateral, or thyroidectomy without any postoperative radioactive iodine administration.”

Meanwhile, in other research, data from the Global Burden of Disease Study has found Australia along with Denmark and the US have increasing thyroid cancer mortality – in stark opposition to the trends in many European countries.

The study, published in JAMA Otolaryngology-Head & Neck Surgery, found 13 of 19 countries had an average annual percentage increase in age-standardised incidence rates across 1990 – 2019.

Australia and the US had the highest average annual percentage change of EU15+ countries across the 30-year study period.

Australia, Denmark, and the US were the only countries with unfavourable, positive average annual percentage changes in mortality rates while the remaining 16 countries had a negative change.

Similarly, disability-adjusted life-years decreased in all EU15+ countries except Australia, Denmark, and the US.

“In the context of the more conservative treatment guidelines and a 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.”

“It is essential the balance is struck between avoiding overdiagnosis and incorrectly managing true disease.”

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