Objective: To determine whether TNF blockers increase tumour risk in patients with RA.
Material and methods: The South Swedish Arthritis Treatment Group register (SSATG) comprises over 90% of anti-TNF treated patients with RA in the area. 757 patients treated with etanercept or infliximab included between 1 February 1999 and 31 December 2002 were identified. 800 patients with conventional antirheumatic treatment in a community based cohort served as a comparison cohort. Tumours and deaths were identified in the cancer registry and population census registers. Patients were followed up from initiation of anti-TNF treatment or 1 July 1997 for the comparison group, until death or 31 December 2002.
Results: In the anti-TNF group, 16 tumours (5 lymphomas) were identified in 1603 person-years at risk, and in the comparison group 69 tumours (2 lymphomas) in 3948 person-years. Standardised incidence ratios (SIRs) for total tumour relative risk for the anti-TNF group and the comparison group were 1.1 (95% confidence interval (CI) 0.6 to 1.8) and 1.4 (95% CI 1.1 to 1.8), respectively. The lymphoma relative risk (RR) was 11.5 (95% CI 3.7 to 26.9) and 1.3 (95% CI 0.2 to 4.5), respectively The total tumour RR excluding lymphoma was 0.79 (95% CI 0.4 to 1.42) and 1.39 (95% CI 1.08 to 1.76), respectively. Proportional hazard analysis for lymphomas yielded RR 4.9 (95% CI 0.9 to 26.2) in anti-TNF treated versus untreated patients.
Conclusion: Community based patients with RA treated conventionally had an increased overall tumour risk compared with the background population. A possible additional increased risk for lymphoma associated with TNF blockers was based on few cases and needs confirmation.