Hydroxychloroquine and risk of cancer in patients with primary Sjögren syndrome: propensity score matched landmark analysis

Hydroxychloroquine inhibits systemic inflammation and autophagy and may thus have antineoplastic effects [1]. We investigated the effect of hydroxychloroquine on cancer risk in patients with primary Sjögren syndrome(pSS). We used the Taiwan National Health Insurance Database to compare cancer incidence between incident pSS patients with or without at least 6-month hydroxychloroquine use within a 1- or 3-year period. Propensity score matched landmark analysis was used. We included 4194 alive patients without cancer 1 year after pSS diagnosis from 2000 through 2005. The propensity score matched 1148 patients with at least 6-month hydroxychloroquine exposure at 1 year after diagnosis and 1148 patients without. Median follow-up after the 1-year landmark was 6 years. During follow up 62 hydroxychloroquine users and 56 non-hydroxychloroquine users developed cancer. Kaplan-Meier estimates showed no difference in overall survival between hydroxychloroquine users and non-users in the 1-year. Hydroxychloroquine was associated with a hazard ratio (HR) of 1.11 (95% CI, 0.78-1.60) in 1-year landmark analysis. In 3-year landmark analysis, hydroxychloroquine was associated with a HR for cancer of 1.37 (95% CI, 0.97-1.94). This propensity score matched landmark analysis of Taiwanese patients with incident pSS found that hydroxychloroquine was not associated with cancer risk nor protection.