Therapy-related lymphomas in patients with autoimmune diseases after treatment with disease-modifying anti-rheumatic drugs.

Ten patients developing lymphomas after disease modifying anti-rheumatic drugs (DMARD) (methotrexate, n = 3, mean cumulative dose = 3.4 g; cyclophosphamide, n = 2, mean dose = 70 g; azathioprine, n = 6, mean dose = 243 g) were investigated. Methotrexate-related lymphomas were Epstein-Barr virus (EBV)-positive, had infrequent aberrant methylation of p15 and p16, and responded well to methotrexate withdrawal or anti-CD20 antibody (rituximab) alone without concomitant chemotherapy, implying that defective immunosurveillance was important in lymphomagenesis. However, 75% of cyclophosphamide/azathioprine-related lymphomas were EBV-negative, had frequent p15 and p16 methylation, and responded poorly to drug withdrawal and chemotherapy, implying that direct drug-induced mutagenesis might be involved in lymphomagenesis.