Incidence and Risk of Malignancy in Japanese Patients With Rheumatoid Arthritis in the National Database of Rheumatic Diseases in Japan (NinJa Database)

Objective

The study aimed to evaluate the incidence rate and potential risk factors of malignancies in Japanese patients with rheumatoid arthritis (RA).

Methods

This retrospective observational study analyzed data of adult patients with RA from April 2013 to March 2019 using the NinJa database. Patients were categorized into the overall RA cohort and sub-cohorts: biologic disease-modifying antirheumatic drug (bDMARDs) or Janus kinase inhibitors (JAKi-s)-exposed, bDMARDs exposed, and bDMARDs or JAKi-s naïve conventional synthetic DMARDs exposed. The incidence of overall and each type of malignancy was calculated, and the associated risk factors were analyzed using multivariate logistic regression.

Results

Overall, 26 607 patients were included in the overall RA cohort (mean age: 64.16 ± 13.29 years; female: 78.87%) with 1018 malignancies. The incidence of malignancies was similar to that in the general population, with a standardized incidence ratio (SIR) of 0.97 (95% confidence interval [CI]: 0.91–1.03). It was consistent across the sub-cohorts and each year. The most frequent malignancies were lung cancer (n = 158), lymphoma (n = 151) and colorectal cancer (n = 145). The incidence of lymphoma and skin cancer was higher than the general population, with SIRs of 4.00 (3.39–4.68) and 1.70 (1.25–2.30), respectively. Multivariate analysis showed older age, male sex, smoking, Steinbrocker stage score 2 versus 1, 4 versus 1, and higher Disease Activity Score 28 using C-reactive protein as potential risk factors for malignancies.

Conclusion

Japanese patients with RA did not have an elevated risk of overall malignancies, whereas the incidence of lymphoma and skin cancer was higher in patients with RA than in the general population.