198. MORTALITY IN PATIENTS WITH RHEUMATOID ARTHRITIS AND INTERSTITIAL LUNG DISEASE TREATED WITH TUMOUR NECROSIS FACTOR INHIBITOR OR RITUXIMAB

Abstract

Background: Pulmonary involvement, including interstitial lung disease (ILD), is common in patients with rheumatoid arthritis (RA) and is associated with increased mortality. Early reports suggested that TNF-α inhibitors (TNFi) may be linked to the development, or exacerbation, of RA-ILD. In 2005 the British Society for Rheumatology advised caution on the use of TNFi for patients with RA-ILD. Conversely, no comparable recommendations for rituximab (RTX) exist, which is often used where contraindications for TNFi exist. This study aimed to examine mortality in patients with RA-ILD who received either TNFi or RTX as their first-line biologic. Methods: Participants in the British Society for Rheumatology Biologics Register for RA with clinician reported RA-ILD at baseline commencing TNFi or RTX as their first biologic were included in this analysis. Date and cause of death were captured on regular study follow-up forms and through linkage with the UK National Death Register. Death rates, per 1000 person-years (pyrs) were calculated (95% CI); censoring occurred at death or 5 years following start of their first biologic, whichever came first. Kaplan-Meier survival curves were generated, with risk comparisons made between the RTX and TNFi cohorts using Cox regression using an ever exposed model, adjusted for potential confounders. The frequency with which ILD was recorded on death certificates was also examined. Results: Of 352 eligible participants with RA-ILD, 310 were treated with TNFi (all recruited ≤2008) and 42 were treated with RTX patients (all recruited >2008). During 5 years of follow-up, there were 76 deaths in 801.3 pyrs in the TNFi cohort and 8 deaths in 150.7 pyrs in the RTX cohort; death rates were 94.8 (74.4-118.7) and 53.0 (22.9-104.6) per 1000 pyrs, respectively. The unadjusted mortality risk in the RTX treated patients was numerically half that in the TNFi treated patients, but not statistically significant (HR 0.53, 95%CI:0.26-1.10). Adjustment for baseline age, sex, disability, disease activity, and disease duration made little difference to the estimate (HR 0.49, 95%CI:0.23-1.06). ILD was recorded on 36.5% of 74 available death certificates from the TNFi cohort and 71.4% of 7 available death certificates from the RTX cohort. Comparable proportions had ILD recorded as the underlying cause of death (RTX=14%, TNFi=16%). Conclusion: Patients with RA-ILD who were selected to receive RTX as their first biologic for RA appeared to have better long-term survival compared to patients who received TNFi, although this difference was not statistically significant. ILD was more commonly recorded on the death certificates of RTX patients, but the proportion of cases in which ILD was the underlying cause of death was comparable. Absence of information on severity or subtype of ILD precludes conclusions regarding the relative safety of these two therapies for RA-ILD and more detailed analysis should be undertaken.