Association between rheumatoid arthritis and thyroid cancer risk: a real-world cohort study using TriNetX.

Objective: To evaluate the association between rheumatoid arthritis (RA) and the risk of developing thyroid cancer using real-world data.

Methods: This retrospective cohort study was conducted in June 2025 using data from the TriNetX Research Network, a global federated health platform aggregating anonymized electronic medical records from 28 healthcare organizations. Patients aged 20-84 years with RA were identified and matched 1:1 to controls without RA using propensity score matching. Two time-windows were used for cancer outcome assessment: primary analysis with 1-year lag and sensitivity analysis with 180-day lag. Additionally, a Cox proportional hazards regression model was applied to estimate adjusted hazard ratio (HR), controlling for age, sex, and comorbidities.

Results: In the primary analysis (1-year lag), 77 of 42,068 patients with RA and 14 of 42,121 controls developed thyroid cancer (cumulative incidence: 0.18% vs. 0.03%; risk ratio: 5.51, 95% CI: 3.12-9.73). In the sensitivity analysis (180-day lag), the association between RA and thyroid cancer remained significant (cumulative incidence: 0.21% vs. 0.05%; risk ratio: 4.36, 95% CI: 2.68-7.08). The Cox model yielded an adjusted HR of 1.40 (95% CI: 1.18-1.67, P < 0.001), further supporting the association between RA and increased thyroid cancer risk.

Conclusion: Rheumatoid arthritis is associated with a significantly elevated risk of thyroid cancer. Further studies are needed to explore underlying mechanisms and guide cancer surveillance strategies in care of patients with rheumatoid arthritis. Key Points • Patients with rheumatoid arthritis experience a significantly increased burden of cancers. • The Cox model yielded an adjusted hazard ratio of 1.40 (95% CI: 1.18-1.67), further supporting the association between rheumatoid arthritis and increased thyroid cancer risk. • Further studies are warranted to explore underlying mechanisms and guide cancer surveillance strategies in care of patients with rheumatoid arthritis.