Trends in risks of malignancies in Japanese patients with rheumatoid arthritis: Analyses from a 14-year observation of the IORRA cohort

Objectives The aim is to investigate the trends in risks of overall and site-specific malignancies in patients with rheumatoid arthritis (RA). Methods Among Japanese patients with RA enrolled in the Institute of Rheumatology, Rheumatoid Arthritis cohort, all malignancies that occurred from 2000 to 2013 were extracted. The standardized incidence ratios and 95% confidence intervals for overall and site-specific malignancies were calculated during three periods: pre-biologics, 2000-04; early biologics, 2005-09; and recent biologics, 2010-13. Risk factors for overall and specific malignancies were analysed using time-dependent Cox regression models. Results Among 11,299 patients with RA (68,483 person-years), 507 malignancies were confirmed. Similar risks were observed versus the general Japanese population for overall malignancies throughout the three periods, with standardized incidence ratios (95% confidence intervals) of 0.96 (0.80-1.14) in the pre-biologics period, 0.95 (0.82-1.09) in the early biologics period, and 0.87 (0.75-1.01) in the recent biologics period. A significantly increased risk for malignant lymphoma was observed throughout the observation period (standardized incidence ratio 4.61, 95% confidence interval 3.58-5.85). The disease activity was a significant risk factor for overall malignancies and lung cancer. Conclusions Despite the expanding use of methotrexate and biologics, there were no increases in malignancy risk in Japanese patients with RA.