The research used data from the TriNetX Research Network, and analyzed anonymized electronic medical records from 28 healthcare organizations across the globe. This study focused on patients aged 20 to 84 years diagnosed with RA, who were compared to a matched control group without RA. To minimize bias, this research applied propensity score matching on demographics and comorbidities, ensuring a fair comparison between the groups.
The team examined thyroid cancer outcomes in a primary analysis with a one-year lag and a sensitivity analysis with a 180-day lag. This approach was designed to account for diagnostic delays and ensure robustness of the findings.
In the primary analysis (one-year lag), 77 out of 42,068 patients with RA were diagnosed with thyroid cancer, when compared with just 14 out of 42,121 controls. This translated to a cumulative incidence of 0.18% in the RA group versus 0.03% in the control group, which represented a 5.5-fold higher risk for RA patients (risk ratio: 5.51, 95% CI: 3.12–9.73).
The sensitivity analysis (180-day lag) reinforced these findings. Here, the cumulative incidence was 0.21% in RA patients compared to 0.05% in controls, equating to a risk ratio of 4.36 (95% CI: 2.68–7.08).
After applying Cox proportional hazards regression model, adjusting for age, sex, and comorbidities, this study found an adjusted hazard ratio (HR) of 1.40 (95% CI: 1.18–1.67, P < 0.001). This confirmed that even after accounting for potential confounders, RA patients underwent a significantly higher risk of developing thyroid cancer when compared to those without RA.
Taken together, the results highlight that rheumatoid arthritis, long associated with systemic inflammation and an increased cancer burden, may also predispose patients to thyroid malignancies. The underlying biological mechanisms remain uncertain, but chronic inflammation, immune dysregulation, and treatment-related factors are likely contributors.
Overall, these findings found that RA patients show a significantly elevated risk of thyroid cancer when compared to non-RA controls across both one-year and 180-day analyses. These results support the need for tailored surveillance strategies, stressing that early detection could prove critical in improving patient outcomes. Given the elevated risks identified, physicians may need to consider more vigilant monitoring of thyroid health in RA patients.
Source:
Lai, S.-W., Kuo, Y.-H., & Liao, K.-F. (2025). Association between rheumatoid arthritis and thyroid cancer risk: a real-world cohort study using TriNetX. Clinical Rheumatology. https://doi.org/10.1007/s10067-025-07668-6
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