Clinicopathological characteristics and rituximab addition to cytotoxic therapies in patients with rheumatoid arthritis and methotrexate-associated large B lymphoproliferative disorders.

AIMS To analyse the clinicopathological characteristics and prognosis of 40 rheumatoid arthritis (RA) patients with methotrexate (MTX)-associated large B cell lymphoproliferative disorders (MTX-BLPD). METHODS AND RESULTS Soluble interleukin 2 receptor titres (median 1500 U/ml) in 40 patients with MTX-BLPD were lower than those of 24 RA patients with non-MTX- associated (non-MTX) BLPD (5731 U/ml) and 15 with control diffuse large B cell lymphoma (DLBCL, 5918 U/ml) (P < 0.01). Using in-situ hybridization, Epstein-Barr virus (EBV) was detected in tumour cells of 25 of 40 RA patients with MTX-BLPD (63%). Immunohistologically, BCL2 expression was detected in 35% of patients with MTX-BLPD, which was lower than 93% of control DLBCL patients (P < 0.01). Eleven patients with EBV(+) MTX-BLPD (44%) showed remission after MTX withdrawal. In RA patients with clinical stage III/IV BLPD, 15 with rituximab (R)+ cytotoxic therapies pursued better prognosis than 10 with R- cytotoxic therapies (P < 0.05). Among the 15 patients, seven with MTX-BLPD showed better overall survival than nine control DLBCL patients (P < 0.01). CONCLUSIONS In RA patients with MTX-BLPD, immunosuppression by MTX, EBV infection and low BCL2 expression in tumour cells may play roles in tumorigenesis and tumour regression. R+ cytotoxic therapies as well as MTX withdrawal were highly effective in these patients.