Cancer incidence and outcome for patients with Rheumatoid Arthritis: a long-term population study in Western Australia.

Abstract

Objective: To compare malignancy incidence and impact between hospitalized patients with Rheumatoid Arthritis (RA) and controls.

Methods: Population-level observational study of patients with RA identified (ICD-9CM 714, ICD10-AM M05-M06) in the Hospital Morbidity Data Collection (HDMC) in Western Australia (WA) between 1985 and 2015 and non-exposed hospitalised controls matched on gender, age and year of index admission. HDMC data were linked to WA Cancer and WA Death Registry data and cancer incidence rates (CIR) per 1000 person years (PY) , incidence rate ratio ratios (IRR) with 95% CI and Kaplan Meier survival estimated.

Results: Among 14.041 patients with RA (67.56 % female, age 65 years) and 33.785 controls (65.16% female, age 65 years), preexisting cancer in RA patients was less prevalent than in controls (7.6% vs 14.2%, p<0.01). In participants without prior cancer, the overall post index CIR was lower in RA (19.68 vs 24.77, IRR 0.79 , CI 0.76-0.83) and stable over three study decades. CIR was higher in RA patients for lung (1.17 , CI 1.04-1.34) and haematological cancer (1.21 , CI 1.03-1.43) but lower for most other cancer types. Median survival was lower for RA patients than controls (overall 3.3 vs 5.3 years, p<0.01) with increased mortality rates observed for most cancer subtypes.

Conclusion: Overall CIR in RA patients was stably lower over time than in matched controls. CIR was only increased for lung and haematological cancer. Despite the overall lower CIR, post cancer mortality was higher for patients with RA in most cancer subtypes.