Lymphoma in RA: the effect of MTX and anti-TNF therapy in 18,572 patients

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Arthritis Rheum. 2004 Jun;50(6):1740-51.

Lymphoma in rheumatoid arthritis: the effect of methotrexate and

anti-tumor necrosis factor therapy in 18,572 patients.

Wolfe F, Michaud K.

National Data Bank for Rheumatic Diseases, Arthritis Research

Foundation, Wichita, KS 67214, USA. fwolfe@...

OBJECTIVE: The risk of lymphoma is increased in patients with rheumatoid

arthritis (RA), and spontaneous reporting suggests that methotrexate

(MTX) and anti-tumor necrosis factor (anti-TNF) therapy might be

associated independently with an increased risk of lymphoma. However,

data from clinical trials and clinical practice do not provide

sufficient evidence concerning these issues because of small sample

sizes and selected study populations. The objective of this study was to

determine the rate of and standardized incidence ratio (SIR) for

lymphoma in patients with RA and in RA patient subsets by treatment

group. Additionally, we sought to determine predictors of lymphoma in

RA. METHODS: We prospectively studied 18,572 patients with RA who were

enrolled in the National Data Bank for Rheumatic Diseases (NDB).

Patients were surveyed biannually, and potential lymphoma cases received

detailed followup. The SEER (Survey, Epidemiology, and End Results)

cancer data resource was used to derive the expected number of cases of

lymphoma in a cohort that was comparable in age and sex with the RA

cohort. RESULTS: The overall SIR for lymphoma was 1.9 (95% confidence

interval [95% CI] 1.3-2.7). The SIR for biologic use was 2.9 (95% CI

1.7-4.9) and for the use of infliximab (with or without etanercept) was

2.6 (95% CI 1.4-4.5). For etanercept, with or without infliximab, the

SIR was 3.8 (95% CI 1.9-7.5). The SIR for MTX was 1.7 (95% CI 0.9-3.2),

and was 1.0 (95% CI 0.4-2.5) for those not receiving MTX or biologics.

Lymphoma was associated with increasing age, male sex, and education.

CONCLUSION: Lymphomas are increased in RA. Although the SIR is greatest

for anti-TNF therapies, differences between therapies are slight, and

confidence intervals for treatment groups overlap. The increased

lymphoma rates observed with anti-TNF therapy may reflect channeling

bias, whereby patients with the highest risk of lymphoma preferentially

receive anti-TNF therapy. Current data are insufficient to establish a

causal relationship between RA treatments and the development of

lymphoma.

PMID: 15188349

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