Hydroxychloroquine had neutral effect on long-term risk of malignancy in rheumatoid arthritis patients: A population-based retrospective cohort study.

Abstract

The cancer risk in rheumatoid arthritis (RA) patients has been discussed. Hydroxychloroquine (HCQ) may exert protective effects against malignancy. The study investigated the association between HCQ use and the risk of subsequent malignancy in RA patients. Catastrophic illness certificated RA patients were extracted from the National Health Insurance Research Database. The index date was set 180 days after the RA diagnosis date to avoid immortal time bias. Two groups were matched in a 1-to-1 ratio by propensity score regarding age, gender, index date, relevant comorbidities, and comedication. HCQ users prior to the diagnosis of RA were exempted to ensure compliance with the new-user design. Cancers diagnosed before or less than 180 days after the index date were excluded to mitigate protopathic bias. The study adopted the Kaplan-Meier curve and Cox proportional hazards model to examine the association between HCQ use and cancer risk. The assumption of proportional hazard was also tested. Based on strict criteria, we included 492 eligible RA patients and divided them into study and control groups (N = 246 in each group). HCQ users exhibited a neutral risk of cancer relative to the controls (adjusted hazard ratio, 0.99; 95% CI, 0.44-2.21, p > .05). The assumption of proportional hazard was not violated. This study does not observe the effect of using HCQ as a primary regimen to prevent cancer in RA patients. We are assured that HCQ is not associated with an increased risk of subsequent malignancy in RA patients. Further mechanistic research is needed.