Malignancy risk in Australian rheumatoid arthritis patients treated with anti-tumour necrosis factor therapy: an update from the Australian Rheumatology Association Database (ARAD) prospective cohort study

Background: Tumour necrosis factor inhibitor (TNFi) therapy has been available for rheumatoid arthritis (RA) patients for several decades but data on the long-term risk of malignancy associated with its use is limited. Our aims were to assess malignancy risk in a cohort of Australian RA patients relative to the Australian population and to compare cancer risk for patients exposed to TNFi therapy versus a biologic-naïve group.

Methods: Demographic data for RA participants enrolled in the Australian Rheumatology Association Database (ARAD) before 31 Dec 2012 were matched to national cancer records in May 2016 (linkage complete to 2012). Standardised incidence ratios (SIRs) were used to compare malignancy incidence in TNFi-exposed and biologic-naïve ARAD participants with the Australian general population using site-, age- and sex-specific rates by calendar year. Malignancy incidence in TNFi-exposed participants and biologic-naïve RA patients, were compared using rate ratios (RRs), adjusted for age, sex, smoking, methotrexate use and prior malignancy.

Results: There were 107 malignancies reported after 10,120 person-years in the TNFi-exposed group (N = 2451) and 49 malignancies after 2232 person-years in the biologic-naïve group (N = 574). Compared with the general population, biologic-naïve RA patients showed an increased risk for overall malignancy (SIR 1.52 (95% confidence interval (CI) 1.16, 2.02) prostate cancer (SIR 2.10, 95% CI 1.18, 4.12). The risk of lung cancer was increased for both biologic naïve and TNFi-exposed patients compared with the general population (SIR 2.69 (95% CI 1.43 to 5.68) and SIR 1.69 (95% CI 1.05 to 2.90) respectively). For the TNFi-exposed patients there was an increased risk of lymphoid cancers (SIR 1.82, 95% CI 1.12, 3.18). There were no differences between the exposure groups in the risk of cancer for any of the specific sites examined.

Conclusions: Overall malignancy incidence was elevated for biologic-naïve RA patients but not for those exposed to TNFi. TNFi exposure did not increase malignancy risk beyond that experienced by biologic-naïve patients. Lung cancer risk was increased for both TNFi-treated and biologic-naïve RA patients compared with the general population suggesting that RA status or RA treatments other than TNFi may be responsible in some way.