To study the risk of a second malignant neoplasm (SMN) and mortality in patients with rheumatoid arthritis (RA) with a history of a primary cancer diagnosis and treated with biological disease-modifying antirheumatic drugs (bDMARD).
Among patients with RA (n=15 286) registered in the DANBIO Register during 2000-2011, 1678 had a primary cancer according to the Danish Cancer Registry. HRs for SMN and death were calculated.
During follow-up there were 279 patients with RA contributing person-years to the bDMARDs use 
Among patients with RA with a history of cancer, treatment with bDMARDs was not associated with increased risk of SMN. No clear conclusion can be drawn regarding mortality in bDMARD-treated patients with RA.