Tumor Necrosis Factor Alpha (TNF-a) Blockade and Risk of Lymphoma: Systematic Review and Analysis of Literature

BACKGROUND: TNF-α plays a critical role in the regulation of cytokine mediated cancer immunosurveillance. Evidence suggests that depletion of TNF-α may result in abrogated anti-tumor immunity and increase in the risk of malignancies. Anti-TNF-α therapy (infliximab, adalimumab and etanercept) is known to halt the progression of certain inflammatory disorders and has been approved for the treatment of at least five autoimmune/inflammatory conditions. Given the widespread use of these biological agents, it is vital to explore the associated increased risk of malignancies especially lymphoma.

OBJECTIVE: Risk of lymphoma associated with anti-TNF-α therapy is controversial in rheumatoid arthritis (RA) and has not been extensively studied in other inflammatory disorders. With the expanding role of anti-TNF-α therapy, we evaluated the risk of lymphoma among all approved indications for which they are currently in use.

METHODOLOGY: We conducted a systematic electronic search of MEDLINE using the terms TNF-α, infliximab, adalimumab, etanercept, rheumatoid, psoriasis, arthritis, inflammatory bowel disease, ankylosing spondylitis from January 1998 to December 2007. Studies analyzed were restricted to those in English language, full text published articles, randomized controlled trials (RCT), meta-analysis (MT), review articles, extension studies, reports from national databases (ND) and postmarketing surveillance studies. Risk of lymphoma from ND was obtained as odds ratio with 95% confidence interval. Incidence of lymphoma reported from RCT was analyzed as percentage fraction of the total number of patients enrolled in the study and follow up.

RESULTS: Overall 51 studies (2 MT, n=10,370; 4 ND, n=29,099 and 45 RCT, n=54,637) that included anti-TNF-α therapy in inflammatory disorders were analyzed. Treatment/follow up period were variable from 12 weeks to 8 years. Ten patients (0.09%) from MT treated with anti-TNF-α therapy developed lymphoma vs 0 in the non-anti-TNF-α group. Report from one of the 3 ND showed an increased risk (11.5 RR 95% CI 3.7–26.9) of lymphoma among the anti-TN-α exposed group. Among the RCT, 16 patients (0.02%) in the anti-TNF-α group developed lymphoma vs 3 (0.005%) in the control group.

CONCLUSION: Existing data suggests that anti-TNF-α therapy in rheumatoid arthritis is associated with an increased risk of lymphoma but this may be attributed to the severity of the disease itself. Among other inflammatory disorders, a rise in lymphoma risk could not be established. Whether anti-TNF-α therapy in the long term can in fact decrease the incidence of lymphoma by altering the disease severity remains to be determined.