Increased risk of malignancy in patients with systemic lupus erythematosus: population-based cohort study in Korea

BACKGROUND: This study aimed to evaluate the crude incidence rates and relative risk of malignancy in Korean patients with SLE. METHODS: We conducted a retrospective nationwide cohort study using databases from the National Health Insurance Service in Korea. All prevalent SLE patients aged over 19 were identified from January 2012 to December 2014 and observed until the diagnosis of malignancy, death, or end of the study, December 2015. The crude incidence rates (IRs) and standardised incidence ratios (SIRs) of overall and site-specific malignancies in SLE patients were estimated. RESULTS: We identified 17,854 SLE patients and during the observation period (60,511 person-years [PYs]), 768 solid malignancies (126.9/10,000 PYs) and 68 haematologic malignancies (11.2/10,000 PYs) occurred in SLE patients. In SLE patients, breast and reproductive system and thyroid cancers occurred predominantly, followed by liver and colon cancers. The SIRs of overall, solid, and haematologic malignancies of SLE patients compared to the general population were 1.8 (95% confidence interval [CI] 1.6–1.9), 1.7 (95% CI 1.5–1.8), and 5.9 (95% CI 4.8–7.3), respectively. In solid malignancies, head and neck (2.7, 95% CI 1.1–4.2), bladder (2.4, 95% CI 1.1–3.8), liver (1.9, 95% CI 1.4–2.3), pancreas (1.9, 95% CI 1.3–2.6), lung (1.8, 95% CI 1.2–2.4), colon (1.7, 95% CI 1.3–2.2), thyroid (1.6, 95% CI 1.3–1.8) and breast and reproductive system (1.5, 95% CI 1.2–1.7) cancers are at increased risk in SLE patients. CONCLUSION: An increased risk of haematologic and solid malignancies was observed in Korean patients with SLE compared to the general population.