To investigate the incidence and clinical features of methotrexate (MTX)-related lymphoproliferative disorders (MTX-LPDs) in patients with rheumatoid arthritis (RA).
In total, 589 RA outpatients were examined at the National Center for Global Health and Medicine in the period from January 1990 to October 2010.
MTX was used in 403 cases, and the duration of follow-up was 2379 person-years. Four patients developed MTX-LPDs; the incidence of MTX-LPDs was calculated as 0.00168/person-year and the standardized incidence as 8.21 (95% CI: 0.16-24.30). The mean total dosage of MTX was 1142 ± 871 mg, and the dosage at LPD onset was 7.4 ± 1.9 mg/week. The patients who developed MTX-LPDs had significantly shorter disease duration of RA compared with the patients who had not received MTX, but who had not progressed to LPDs (3.1 years vs. 12.5 years; P = 0.01). The following LPD subtypes were observed: diffuse large B-cell lymphoma (N = 2); Hodgkin's lymphoma (N = 1); and T-cell lymphoma (N = 1). After withdrawal of MTX, two of these patients showed spontaneous regression of the tumor, one did not have a recurrence, while the other patient relapsed and required chemotherapy.
Our study revealed that MTX-LPDs are not rare complications of RA outpatients. The MTX-LPDs were associated with a relatively shorter RA duration, and half of them showed tumor regression after MTX withdrawal, which suggested an association with MTX. It is important to consider the possibility of MTX-LPD in RA patients who have received MTX.