OBJECTIVE: To investigate the risk of virus-associated cancer in female arthritis patients ever treated with biological DMARDs (bDMARDs) compared with never bDMARD-treated patients and ever and never treated with bDMARD compared with the general population.

METHODS: This was a cohort study that included 13 905 female patients with RA (72%), PsA (12%), AS (4%) or other arthritides (12%) identified in the DANBIO registry. Ever (n = 5647) and never (n = 10 331) bDMARD-treated patients were followed for virus-associated cancers during 2000-11 by linkage to the Danish Cancer Registry. Hazard ratios and standardized incidence ratios (SIRs) were calculated.

RESULTS: In total, 24 and 32 virus-associated cancers were identified among ever and never bDMARD users, respectively (hazard ratio = 0.9, 95% CI: 0.7, 1.2). Oropharyngeal (n = 3, SIR = 4.0, 95% CI: 1.3, 12.4) and anal (n = 2, SIR = 2.5, 95% CI: 0.6, 10.0) cancer only occurred among bDMARD-treated patients. SIR was not increased for cervical cancer, either in ever or never bDMARD-treated patients. SIRs for Hodgkin's and non-Hodgkin's lymphomas were increased in never bDMARD-treated patients (SIR = 2.5, 95% CI: 1.5, 4.0).

CONCLUSION: bDMARD therapy was not associated with an overall excess of virus-associated cancers in female arthritis patients. The observed increased occurrence of oropharyngeal cancer needs further investigation. Lymphoma incidence was increased in patients unexposed to bDMARD treatment.