An alternative practice, substituting the immunomodulator MTX for a thiopurine in combination with biologic therapy, warrants consideration. In a recent review examining the long-term safety of MTX therapy in RA, Salliot and van der Heijde concluded that there did not seem to be an increased risk of lymphoma in adults receiving MTX monotherapy with mean dose of 10.5 mg weekly (range: 4.6–18 mg).[79] The majority of experience of combination biologic therapy with MTX arises from the rheumatology literature, where a biologic is almost always used in combination with MTX. Although the clinical trial literature has suggested a potential link between anti-TNF therapy and lymphoma,[80] longer-term RA studies suggest there is no association. Wolfe and Michaud led a large observational study of lymphoma in 19,562 adult patients, which included over 89,710 person-years of follow-up including anti-TNF exposure in 10,815 patients. This study found no evidence supporting a link between anti-TNF therapy, MTX or combination therapy and the risk of lymphoma in routine clinical practice.[70] This study is in agreement with an analysis of the linked cancer registry reports from adults with RA in Sweden by Askling et al..[68] Pediatric juvenile idiopathic arthritis (JIA) observational studies provide further reassurance.[69,81] Beukelman et al. observed 7812 children with JIA with 12,614 person-years follow-up. The standardized incidence ratio (SIR) for probable and highly probable malignancies was 4.4 (95% CI: 1.8–9.0) in children with JIA versus children without JIA. The treatment for JIA, including MTX monotherapy (SIR: 3.9 [95% CI: 0.4–14]) and TNF inhibitors (SIR: 0 [95% CI: 0–9.7]) did not appear to be significantly associated with the development of malignancy.[69] Most of the studies in the rheumatologic literature do not account for RA severity. This could be important because natural history studies in RA have exhibited an increased risk of lymphoma in comparison with the general population, primarily thought to be linked to high levels of disease activity.[68–70,80,82–84] In summary, large recent population-based studies primarily in adults with RA provide us with reasonable reassurance of the lack of an association between MTX and anti-TNF and lymphoma. However, analyses controlling for disease severity in adults and children with RA and JIA have been more difficult to conduct. Continue Reading