Risk of malignancy in Korean patients with primary Sjogren's syndrome

Objectives To evaluate the risks of overall and site-specific malignancies in Korean patients with primary Sjogren's syndrome (pSS). Methods Using the Korean nationwide healthcare claims database, we constructed a retrospective cohort for prevalent pSS aged over 50 years. After enrollment between January 2012 and December 2014, patients were followed until the development of any malignancy, or until December 2015. Crude incidence rates of malignancies of pSS patients were calculated, and their standardized incidence ratios (SIRs) for malignancies were calculated compared to those in knee osteoarthritis (OA) patients. Results A total of 6,359 pSS and 5,476,302 knee OA patients were included in this study. During follow-up (19,474 person-years [PYs]), 310 cases of solid malignancy (158.8/10,000 PYs) and 47 cases of hematologic malignancies (23.5/10,000 PYs) were observed in pSS patients. The risks of overall (SIR 1.30, 95% CI 1.16-1.43), solid (SIR 1.16, 95% CI 1.03-1.29), and hematologic malignancies (SIR 4.80, 95% CI 3.43-6.17) were increased in pSS patients. There was an elevated risk of site-specific malignancy in non-Hodgkin's lymphoma (NHL, SIR 6.45, 95% CI 4.05-8.83), multiple myeloma (SIR 4.88, 95% CI 2.00-7.76), and oropharynx (SIR 4.16, 95% CI 1.90-6.42). The risk of lung cancer was increased only in male pSS patients (2.50, 95% CI 1.02-3.99), while the risk of thyroid cancer was increased in female patients (1.44, 95% CI 1.04, 1.84). Conclusion In patients with pSS over age 50, the risk of solid cancers such as oropharynx, thyroid, and lung cancers is also increased in addition to NHL.