Meta-analysis finds rheumatoid arthritis associated with increased thyroid cancer risk in pooled cohort data

Rheumatoid Arthritis (RA), as a common autoimmune disease, not only causes damage to the joints themselves, but also increases the risk of developing other diseases. In recent years, the association between RA and malignant tumors has attracted increasing attention. Most studies have found that RA is associated with site-specific alterations in malignancy risk rather than a uniformly increased risk of all cancers. However, the risk of thyroid cancer in RA patients remains controversial. Different studies even yield contradictory results. Notably, to date, no systematic review or meta-analysis has specifically evaluated this association. Therefore, this meta-analysis aimed to estimate the association between RA and the risk of thyroid cancer, providing evidence for clinical cancer surveillance strategies. The search was conducted from database inception to October 2025 in PubMed, EMBASE, and Web of Science databases. Studies that estimated the association between rheumatoid arthritis (RA) and the incidence of thyroid cancer using hazard ratio (HR) or standardized incidence ratio (SIR) and 95% confidence interval (CI) were included. Two researchers independently screened the literature, extracted the data, and evaluated the risk of bias of the included studies. Meta-analysis was performed using RevMan 5.3 software. This meta-analysis was registered on the PROSPERO platform (CRD420251267552). A total of fourteen cohort studies were included, involving 1,970,165 participants. The meta-analysis indicated that patients with RA have a higher risk of developing thyroid cancer compared to the general population (HR = 1.28, 95%CI: 1.05-1.55, P = 0.01). The subgroup analysis showed that RA in the Chinese population increased the risk of thyroid cancer (HR = 1.79, 95% CI: 1.26-2.54, P = 0.001). There was no association between RA in other populations and the risk of thyroid cancer (HR = 1.01, 95% CI: 0.85-1.21, P = 0.88). RA did not increase the risk of thyroid cancer under parsimonious adjustment (adjusted only for age and/or sex) (HR = 1.03, 95% CI: 0.73-1.44, P = 0.88), but was associated with an increased risk of thyroid cancer under extended adjustment (HR = 1.38, 95% CI: 1.09-1.73, P = 0.006). The existing evidence suggests that RA may be associated with the risk of thyroid cancer. Given the limitations of this study, well-designed prospective studies with appropriate confounding controls are needed to further verify this association. https://www.crd.york.ac.uk/prospero/, identifier CRD420251267552.