POS0061 THE RISK OF LUNG CANCER IN RHEUMATOID ARTHRITIS AND IN RELATION TO AUTOANTIBODY POSITIVITY AND SMOKING

Abstract

BackgroundLung cancer is a common malignancy in rheumatoid arthritis (RA)1,2. Since smoking is a risk factor for both (seropositive) RA and lung cancer, it remains unclear whether RA, in itself, increases lung cancer risk.ObjectivesThe aim of this study was to examine whether and to what extent the increased risk of lung cancer in RA may (or may not) be attributable to smoking, and to examine this association, both in terms of absolute and relative risks, specifically in relation to RA serostatus.MethodsWe performed a population-based cohort study of RA patients and individually matched general population reference individuals identified in Swedish registers and from the EIRA early RA study, prospectively followed for lung cancer occurrence 1995 through 2018. We calculated incidence rates and performed Cox regression to estimate hazard ratios (HR) including 95% confidence intervals (CI) of lung cancer, taking smoking and sero-status into account.ResultsOverall, we included 44,101 RA patients (590 incident lung cancers, 56 per 100,000), and 216,495 matched general population individuals (1,691 incident lung cancers, 33 per 100,000), corresponding to a crude HR (95% CI) of 1.76 (1.60-1.93). In subset analyses this increased risk remained after adjustment for smoking (HR=1.77, 95% CI 1.06-2.97). Compared to general population subjects who were never smokers, RA patients who were ever smokers had almost 7 times higher risk of lung cancer.Positive autoantibody status was associated with an at least doubled risk of lung cancer in ACPA positive patients (vs. ACPA negative patients) and double seropositive (vs. double seronegative) patients after adjusting for comorbidities and smoking (Table 1).Table 1.Number of events, person-years of follow-up, number of events per 100,000 person-years, and relative risk of lung cancer according to autoantibody status in the EIRA sub-cohort. Five Hazard ratios are presented: a) crude; b) adjusted for age, sex, index year, county of residency (model A); c) age, sex, index year, county of residency and comorbidities (renal failure, heart failure, ischemic heart disease, COPD, respiratory infections, hospitalization) (model B) c) all the above plus smoking (model C) and d) as model C with packet-years instead of smoking ever vs. never.No of events (person years of follow-up; No of events/100 000 person years)Crude Hazard ratio (95% CI)Model A Hazard ratio* (95% CI)Model BHazard ratio** (95% CI)Model CHazard ratio** (95% CI)Model D with smoking as pack-years instead of ever/neverPositiveNegativeRF (N=2060)30(49,440; 60.7)6(49,440; 12.1)2.78 (1.16-6.69)3.01 (1.25-7.26)2.82 (1.17-6.82)2.44 (1.01-5.89)2.16 (0.88-5.28)ACPA (N=2060)30(49,440; 60.7)6(49,440; 12.1)3.13 (1.30-7.51)3.43 (1.42-8.25)3.22 (1.33-7.77)2.88 (1.19-6.95)3.29 (1.26-8.58)RF and/or ACPA (N=2060)34(49,440; 68.8)2(49,440; 4.0)6.38 (1.53-26.56)7.62 (1.83-31.83)7.20 (1.72-30.11)6.29 (1.51-26.30)5.76 (1.37-24.21)RF and ACPA (positive vs. double negative)(N=1608)26(38,592; 67.4)2(38,592; 5.2)6.67 (1.58-28.08)7.92 (1.87-33.50)7.08 (1.67-29.98)6.21 (1.47-26.33)5.86 (1.37-25.01)The average absolute five-year risk of lung cancer counting from RA diagnosis was 1.3% in ever-smoking seropositive RA. At 20 years the risk was almost 3% in RA overall, and over 4% for patients who were ever smokers and had at least one autoantibody.ConclusionRA seropositivity is a strong and at least seemingly independent risk factor for lung cancer in RA. The absolute risks point to the potential for regular lung cancer screening, at least in seropositive RA.