AimThe broad aim of this thesis was to explore the risk of malignancy in people with rheumatoid arthritis (RA), treated with anti-tumour necrosis factor (TNF) drugs.MethodsThis thesis used data from patients with RA registered with the British Society of Rheumatology Biologics Register-RA. The risk of cancer in biologic-naive patients treated with traditional disease modifying drugs (nbDMARD) was compared to that in the general population by calculating standardised incidence ratios (SIR). The influence of anti-TNF on cancer risk was then explored by comparing the risk in the anti-TNF cohort to that in the nbDMARD cohort using Cox proportional hazard models.ResultsThe risk of cancer was increased in the nbDMARD cohort by 28% compared to the general population (SIR 1.28, 95% confidence interval (CI) 1.10, 1.48). Risks of lung cancer (SIR 2.39, 95% CI 1.75, 3.19), Hodgkin lymphoma (SIR 12.82, 95% CI 4.16, 29.92) and Non-Hodgkin Lymphoma (SIR 3.12, 95% CI 1.79, 5.07) were increased compared to the general population and both prostate cancer and cancers of the female genital organs reduced; SIRs 0.35 (95% CI 0.11, 0.82) and 0.35 (95% CI 0.10, 0.90) respectively. There was no difference in the risk of cancer in patients treated with anti-TNF compared to nbDMARD, after adjusting for differences in baseline characteristics; Hazard ratio for lymphoma: 1.00 (95% CI 0.49, 2.05); cancers of the solid organs: 0.83 (95% CI 0.64, 1.07); and keratinocyte skin cancer: basal cell carcinoma 1.06 (95% CI 0.64, 1.75), squamous cell carcinoma 1.62 (95% CI 0.44, 5.90). ConclusionsSubjects with RA, treated with nbDMARD were at increased risk of cancer compared to the general population. In particular, lung cancer, lymphoma and KSC were increased. Treatment with the TNF inhibitors ETA, INF or ADA was not associated with a difference in relative risk of lymphoma, solid cancer or skin cancers when compared to nbDMARD.