Risk of second malignant neoplasm and mortality in patients with rheumatoid arthritis treated with biological DMARDs: a Danish population-based cohort study

Objective 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). Methods Among patients with RA (n=15286) 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. Results During follow-up there were 279 patients with RA contributing person-years to the bDMARDs use before their primary cancer diagnosis, 220 to the only after, 92 to the both before and after, while 1203 patients with RA contributed to the non-use strata. Ever use of bDMARDs was associated with a HR of 1.11 (95% CI 0.74 to 1.67) for developing a SMN compared with non-use (cancer site adjusted). The HR for death associated with bDMARD use before the primary cancer diagnosis was increased 1.53 (95% CI 1.13 to 2.09). After further adjustment for extent of the primary cancer, the HR for death was 1.20 (95% CI 0.88 to 1.63) for bDMARDs use before cancer, 1.36 (95% CI 0.78 to 2.39) for bDMARD use only after cancer and 1.22 (95% CI 0.70 to 2.13) for use both before and after the cancer. Conclusions 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.