Abstract
Objective
To determine cancer risk in a cohort of 459 rheumatoid arthritis (RA) patients treated with methotrexate in community practice.
Methods
All RA patients who started methotrexate prior to June 1986 and were attending 1 of 6 rheumatologists were studied. Demographic data were matched to the State Cancer Registry to identify all malignancies (except nonmelanoma skin cancer) for 1983โ1998, and to the National Death Index to identify all deaths to the end of 1999. Followup started on the date when methotrexate was started and ended either on the last confirmed date on which the patient was seen by the rheumatologist or at death. Standardized incidence ratios (SIRs) were calculated using state population cancer rates stratified by sex, age (in 5โyear groups), and calendar year.
Results
There were 4,145 personโyears of followup (average 9.3 years). Eightyโseven malignancies were identified (14 before, 64 during, and 9 after the followup period). There was an estimated 50% excess risk of malignancy among methotrexateโexposed RA patients relative to the general population (SIR 1.5, 95% confidence interval [95% CI] 1.2โ1.9), with a 3โfold increase in melanoma (SIR 3.0, 95% CI 1.2โ6.2), a 5โfold increase in nonโHodgkin's lymphoma (SIR 5.1, 95% CI 2.2โ10.0), and an almost 3โfold increase in lung cancer (SIR 2.9, 95% CI 1.6โ4.8).
Conclusion
Compared with the general population, methotrexateโtreated RA patients have an increased incidence of melanoma, nonโHodgkin's lymphoma, and lung cancer. There may be a role for regular skin cancer screening for all RA patients, particularly those receiving immunosuppressive therapy.