Review of United States data on neoplasms in rheumatoid arthritis.

Relatively sparse literature developed during the past 30 years that sought to characterize the relationship of rheumatoid arthritis to neoplasms. The past decade has seen added concern over possible oncogenic effects of cytotoxic agents now used to manage some patients with rheumatoid arthritis. Acquisition of unambiguous data is complicated by the fact that the cumulative incidence of cancer in the general population exceeds 30 percent, and that most studies have insufficient patient numbers, duration follow-up, and attention to age, sex, race, or known etiologic agents. Thus, it is not surprising to find reports that cancer incidence is high, low, or unchanged in rheumatoid arthritis. Although equally ambiguous data were accumulated concerning potential neoplasm-inducing effects of cytotoxic drugs, concern is justified in relation to increased frequency of bladder cancer after cyclophosphamide and acute leukemia following alkylating agents.