Incidence of malignancy and the risk of lymphoma in Japanese patients with rheumatoid arthritis compared to the general population

Abstract

Objective: Recent advances in the management of patients with rheumatoid arthritis (RA) increased the rates of disease remission and patient life expectancy, while malignancy has become a more common cause of death. Here, we report the incidence of malignancy in a nationwide survey of Japanese patients with RA compared to the general population, focusing on the risk of lymphoma, which often arises in patients with RA.

Methods: Data on the occurrence of malignancy were collected from patients registered in a nationwide Japanese cohort database, the National Database of Rheumatic Diseases by iR-net in Japan, from 2003 to 2012. To adjust for different population composition and to compare the incidence of malignancy with the general population, standardized incidence rates (SIR) were calculated. To identify risk factors for lymphoma, individual patient data were obtained for multivariate analysis for the year before lymphoma diagnosis.

Results: In 10 years, the cohort composed of 66,953 patient-years yielded 559 malignancies, most frequently lung cancer, followed by gastric cancer, breast cancer, and lymphoma. The overall incidence of malignancies in patients with RA was slightly lower than in the general population (SIR 0.89, 95% CI 0.82-0.97). However, lymphoma risk was significantly higher (SIR 3.43, 95% CI 2.59-4.28), whereas risk of colon, rectal, or liver cancer was lower. Significant risk factors for lymphoma were the use of methotrexate or tacrolimus, and higher age.

Conclusion: Patients with RA had no higher overall incidence of malignancies, but lymphoma was significantly more frequent than in the general population.

Keywords: CANCER; EPIDEMIOLOGY; LYMPHOMA; METHOTREXATE; RHEUMATOID ARTHRITIS.