# Overdiagnosis of Papillary Thyroid Cancer

## TL;DR

This study estimates that 72-94% of papillary thyroid cancer cases in the US from 1991 to 2019 were overdiagnosed, suggesting that reducing unnecessary ultrasounds could lower incidence without affecting mortality.

## Contribution

The study quantifies the magnitude of thyroid cancer overdiagnosis in the US and evaluates the impact of reducing ultrasonography use.

## Key findings

- Between 72% and 94% of papillary thyroid cancer cases in the US were overdiagnosed from 1991 to 2019.
- Reducing thyroid ultrasonography use could decrease PTC incidence by 17-41% with negligible impact on mortality.
- Overdiagnosis rates were higher in women both proportionally and absolutely compared to men.

## Abstract

This study uses a validated mathematical simulation model to estimate the overdiagnosis rate of papillary thyroid cancer from 1991 through 2019 in the US.

What proportion of papillary thyroid cancer (PTC) cases were overdiagnosed between 1991 and 2019, and what might be the implications of reducing thyroid ultrasonography use for PTC incidence and overall mortality in the US?

In this study, a simulation model that accounted for changes in incidence during the study period estimated that between 72% and 94% of PTC cases were overdiagnosed in the US between 1991 and 2019. Reducing thyroid ultrasonography for nonpalpable nodules would decrease PTC incidence, with a negligible change in overall mortality.

The finding that thyroid cancer overdiagnosis remained substantial despite accounting for a true increase in incidence suggests that reducing ultrasonography referrals for nonpalpable nodules could help mitigate overdiagnosis.

The magnitude of thyroid cancer overdiagnosis in the US, accounting for the true increase in underlying disease, has not been quantified. The implications of reducing thyroid ultrasonography use for these rates has not been calculated.

To estimate US population-level rates of papillary thyroid cancer (PTC) overdiagnosis, and to identify the implications of reducing thyroid ultrasonography use for thyroid cancer incidence and overall mortality.

This study used a validated simulation model (Papillary Thyroid Carcinoma Microsimulation Model) of contemporary PTC incidence in the adult US population between 1991 and 2019. Data analysis was conducted from June 2024 to August 2025.

Thyroid cancer incidence and referrals for ultrasonography of nonpalpable thyroid nodules.

Model-estimated relative and absolute rates of PTC overdiagnosis, stratified by sex. The model estimated changes in the rates of thyroid cancer incidence and overall mortality if ultrasonography rates were reduced.

The simulation included all adults, aged 18 years or older, in the US. Between 1991 and 2019, the model estimated that 72% to 94% of PTC cases were overdiagnosed. While the proportion of overdiagnosis was slightly higher for women compared with men (75%-95% vs 63%-90%), the absolute rate of overdiagnosis was higher among women compared with men (13-17 per 100 000 individuals vs 3-5 per 100 000 individuals). This rate translated into 443 212 to 573 705 women and 107 804 to 154 504 men who were overdiagnosed with PTC over 28 years. Reducing use of thyroid ultrasonography for nonpalpable nodules by 33% and 67% would have decreased PTC incidence by 17% (18 to 15 per 100 000 individuals) and 41% (18 to 11 per 100 000 individuals) in 2019, respectively, a less than 0.1% change in overall mortality.

This study found that thyroid cancer overdiagnosis in the US remains substantial, even after accounting for possible increases in true incidence. This finding suggests an opportunity to reduce unnecessary thyroid ultrasonography referrals, particularly for nonpalpable nodules, and to reduce unnecessary diagnoses and treatment-related harms without increasing mortality.