Cancer Risk in Patients With Systemic Sclerosis: A Nationwide Cohort Study in South Korea 2004 to 2021.

Objective: Systemic sclerosis (SSc) is a rare autoimmune disease characterized by tissue fibrosis, vasculopathy, and immune dysregulation. Our objectives were to quantify the overall and site-specific cancer risks in patients with SSc compared to the general population, examine temporal trends in cancer incidence following SSc diagnosis, and explore potential associations with immunosuppressive agent use.

Methods: Using data from the Korean National Health Insurance Service, we identified 6,386 patients newly diagnosed with SSc between 2004 and 2020. Standardized incidence ratios (SIRs) were calculated to compare the risk of cancer between patients with SSc and the general population. Subgroup analyses were performed based on age at diagnosis, follow-up duration, and immunosuppressive agent use.

Results: Most patients (80.2%) were women, with a mean ± SD age at diagnosis of 53.1 ± 13.4 years. Patients with SSc had higher risks of overall cancer (SIR 3.12; 95% confidence interval [CI] 2.92-3.33), solid cancer (SIR 3.07; 95% CI 2.86-3.28), and hematologic cancer (SIR 5.70; 95% CI 4.50-7.11) compared to the general population. Myelodysplastic syndrome (SIR 12.52; 95% CI 7.00-20.65) had the highest risk, followed by multiple myeloma, eye, Hodgkin lymphoma, and larynx cancers. Cancer risk peaked among patients aged 20 to 39 years (SIR 5.27; 95% CI 4.31-6.38) and during the first year after diagnosis (SIR 4.44; 95% CI 3.81-5.14).

Conclusion: In this study, we revealed that the incidence of cancer is higher in patients with SSc in South Korea compared to the general population. The strong association between SSc and cancer occurrence prompts clinicians to conduct careful cancer screening for patients with SSc.