Rheumatology · Medical Literature
Meta-analysis and systematic review: the association between rheumatoid arthritis and the risk of thyroid cancer.
Abstract
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.
Clinical relevance
Does a diagnosis of rheumatoid arthritis independently increase the incidence risk of thyroid cancer compared with the general population or unaffected controls, as quantified by pooled hazard ratios or standardized incidence ratios across available observational studies? __SNAPSHOT__ {"studyDesign":"Systematic review with meta-analysis of observational studies (cohort studies and registry-based studies reporting hazard ratios or standardized incidence ratios)","setting":"International; multi-database search of PubMed, EMBASE, and Web of Science from inception to October 2025","sampleSize":"Not reported (number of included studies and total pooled participants not available in the truncated abstract)","population":"Adults with a confirmed diagnosis of rheumatoid arthritis (RA), compared with general population controls or matched non-RA cohorts, across studies reporting incident thyroid cancer","intervention":"Exposure: diagnosed rheumatoid arthritis (an autoimmune, chronic inflammatory disease)","comparator":"General population (standardized incidence ratio studies) or matched non-RA cohorts (hazard ratio studies)","primaryOutcome":"Incidence of thyroid cancer in patients with RA, estimated via pooled hazard ratio (HR) or standardized incidence ratio (SIR) with 95% confidence intervals","followUp":"Not reported (varied by individual included studies; database search covered studies through October 2025)","fundingSource":"Not reported"}
Key findings
The specific pooled HR, SIR, confidence intervals, p-values, I² heterogeneity statistic, number of included studies, total patient-years of follow-up, and results of any subgroup or sensitivity analyses are NOT reported in the available truncated abstract. The abstract states that the meta-analysis was conducted to resolve conflicting and 'even contradictory' findings from prior individual studies on the RA–thyroid cancer association, and that to date no prior systematic review or meta-analysis had specifically evaluated this question. The direction and magnitude of the pooled effect estimate, NNT/NNH, and any assessment of publication bias cannot be reported from the information provided. No adverse event data are applicable to this observational meta-analysis. All quantitative results are not reported based on the available abstract.
Practice implications
IMPORTANT CAVEAT: Only a truncated abstract was available for this summary; the full text, including all quantitative results, was not accessible. What the abstract establishes is the rationale for the study—that individual prior studies have yielded inconsistent, and in some cases contradictory, estimates of thyroid cancer risk in RA patients, and that this is the first dedicated systematic review and meta-analysis to synthesize this specific association. It does NOT—based on the available abstract—establish the direction or magnitude of the association, which patient subgroups (e.g., by sex, serostatus, disease duration, or treatment class) may be at differential risk, or whether findings are clinically actionable. Context from the existing literature is relevant: a Korean population-based cohort found thyroid cancer risk was elevated in male but not female RA patients; a nationwide Danish cohort found no significant increase in thyroid cancer risk across serologic and demographic subgroups; and a real-world TriNetX analysis found a significantly elevated thyroid cancer risk in RA patients. This background heterogeneity underscores both the importance and the complexity of the question this meta-analysis sought to address. The clinical applicability of these results cannot be assessed without the full quantitative output of the pooled analysis. __LIMITATIONS__ 1. Only a truncated abstract is available; no quantitative findings, study-level data, or methodological detail can be evaluated. 2. Observational studies pooled via meta-analysis are inherently susceptible to confounding by indication, surveillance bias (RA patients may undergo more frequent thyroid imaging due to elevated clinical suspicion or co-occurring autoimmune thyroid disease), and ascertainment heterogeneity across registries and healthcare systems. 3. The included studies likely vary substantially in RA ascertainment method, thyroid cancer diagnostic criteria, lag-time methodology, covariate adjustment, and follow-up duration—all potential sources of statistical and clinical heterogeneity. 4. Prior individual studies have yielded contradictory results, raising the possibility of substantial between-study heterogeneity that may limit the interpretability of a pooled estimate. 5. Confounding by DMARDs and biologic therapies (particularly JAK inhibitors, which in a separate meta-analysis were associated with markedly elevated thyroid cancer risk, RR 7.51) cannot be adequately controlled in most observational datasets. 6. Sex-specific effects may be obscured in pooled analyses without appropriate stratification. 7. Generalizability may be limited if included studies are predominantly from East Asian populations where thyroid cancer screening intensity differs markedly from Western settings. 8. Funding source is not reported, precluding assessment of potential sponsorship bias. __BOTTOM_LINE_CATEGORY__ low_certainty __BOTTOM_LINE__ This is the first systematic review and meta-analysis specifically designed to estimate the association between rheumatoid arthritis and thyroid cancer incidence, addressing a clinically important but previously unresolved question. Quantitative results are not available from the truncated abstract; clinicians should access the full publication before incorporating findings into cancer surveillance decision-making for RA patients. Until the pooled estimates and heterogeneity data are reviewed, existing evidence remains conflicting and insufficient to recommend routine thyroid cancer surveillance specifically for RA patients beyond standard clinical care.