Organ-specific digestive system cancer risks in idiopathic inflammatory myopathies: a systematic review and meta-analysis

Abstract Although idiopathic inflammatory myopathies (IIMs) are known to confer an increased malignancy risk, the organ specificity and methodological reliability of digestive cancer estimates remain uncertain. Prior syntheses rarely applied structured risk-of-bias assessment or systematically explored sources of confounding, limiting interpretability. We aimed to generate organ-specific risk estimates for major digestive system cancers in IIMs using a systematic review and meta-analytic framework incorporating structured risk-of-bias assessment. Following PRISMA 2020, we searched PubMed, Embase, Web of Science, and Scopus through 1 September 2026 (PROSPERO CRD420251168712). Observational studies reporting relative risks for digestive system cancers in IIMs were included. Random effects models generated pooled estimates with 95% CIs. ROBINS-E was used to appraise the risk of bias; subgroup, sensitivity, and publication bias analyses were performed. Thirteen studies were included, of which 12 (92.3%) were cohort studies. IIMs were associated with significantly elevated risks for all five major digestive cancers: esophageal (RR = 4.94, 95% CI 1.64–14.82), pancreatic (RR = 3.54, 95% CI 2.55–4.92), gastric (RR = 2.78, 95% CI 1.47–5.27), colorectal (RR = 2.60, 95% CI 1.57–4.30), and hepatobiliary (RR = 2.44, 95% CI 1.69–3.53) cancers. Dermatomyositis showed the strongest associations. Sensitivity analyses showed generally consistent findings; for esophageal cancer, exclusion of one influential study reduced heterogeneity and yielded a lower but still significant pooled estimate (RR = 3.05, 95% CI 2.57–3.62). This systematic review and meta-analysis suggests distinct organ-specific patterns of digestive cancer risk in IIMs and explores factors associated with heterogeneity across studies. Although residual confounding cannot be excluded, these findings may help inform future research on risk-stratified cancer surveillance strategies.