Objective: To investigate the incidence and clinical features of methotrexate (MTX)-related lymphoproliferative disorders (MTX-LPDs) in patients with rheumatoid arthritis (RA).
Patients: 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.
Results: 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.
Conclusion: 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.
Keywords: Incidence; Lymphoproliferative disorder; Methotrexate; Rheumatoid arthritis.