Risk of Overall Malignancies in Korean Patients with Primary Sjögren Syndrome

Abstract

Background/Purpose: A significant association has been found between primary Sjögren syndrome (pSS) and non-hodgkin’s lymphoma (NHL), but few studies have been conducted to explore the association of pSS with the risk of overall malignancies. We conducted the study to investigate the association between pSS and the risks of malignancy including overall and site-specific malignancies.

Methods: Using the Korean nationwide claims database, a retrospective cohort of prevalent pSS patients between January 2012 and December 2014 was constructed. After exclusion of patients who had a previous history of malignancy, each patient was observed up to the development of any malignancy, or December 2015. The crude incidence rate (IR) of overall and site-specific malignancies in patients with pSS over 19 years old was estimated. To assess excess occurrence of overall malignancies in patients over 50 years of age, we calculated standardized incidence ratios (SIR) by dividing the observed number of malignancies of pSS patients by the expected number of malignancies calculated from the accumulated person-years and the age-, sex-, calendar period-specific malignancy incidence rates of knee OA patients.

Results: A total of 9,826 patients with pSS over 19 years of age were enrolled in this study. During 30,082 person-years (PYs) of observation, 424 cases of solid malignancies (IR 140.6/10,000 PYs) and 62 cases of hematologic malignancies (IR 20.2/10,000 PYs) occurred in adult pSS patients. For patients with pSS aged over 50 (n=6,359), 314 cases of solid malignancy (IR 160.8/10,000 PYs) and 42 cases of hematologic malignancies (IR 21.0/10,000 PYs) were diagnosed during 19,474 PYs of follow-up. For the patients over 50 years of age, the SIRs of overall (1.29, 95% CI 1.16-1.43), solid (1.21, 95% CI 1.07-1.34), and hematologic malignancies (4.54, 95% CI 3.17-5.92), in patients with pSS increased compared to those of OA patients (n=5,476,302). Patients with pSS were at a significantly increased risk of non-hodgkin’s lymphoma (SIR 5.75, 95% CI 3.58-7.92), multiple myeloma (SIR 4.88, 95% CI 2.00-7.76), lung cancer (SIR 1.59, 95% CI 1.08-2.09), and lip and oropharyngeal cancer (SIR 4.16, 95% CI 1.90-6.42).

Conclusion: Our study indicates that pSS is significantly associated with increased risks of overall malignancy, NHL, multiple myeloma, lung cancer, and lip and oropharyngeal cancer.