Clinical outcomes of patients with diffuse large B-cell lymphoma and concomitant rheumatoid arthritis: a nationwide Danish register-based cohort study.

Objectives: This register-based cohort study aimed to investigate clinical cancer outcomes in patients with rheumatoid arthritis (RA) who develop diffuse large B-cell lymphoma (DLBCL) compared with those in patients without RA but with DLBCL. Methods: The study included all patients with RA and DLBCL aged ≥18 years in the Danish National Lymphoma Registry who received first-line treatment between January 1, 2006, and May 21, 2022. RA diagnoses (exposure) and patients without RA (comparator) at the time of DLBCL diagnosis were identified through linkage with the Danish Rheumatology Quality Register and the Danish National Patient Registry. Patients were followed up from DLBCL treatment initiation until emigration, death, outcomes of interest, or May 21, 2022. Hazard ratios (HRs) and 95% CIs were estimated for outcomes including overall survival (OS), progression-free survival (PFS), and hospital admissions. Results: The final study cohort included 136 patients with RA and 5372 without RA. Adjusted HRs for OS and PFS in patients with RA were 1.02 (95% CI, 0.74-1.39) and 0.86 (95% CI, 0.65-1.14), respectively, compared with those of patients without RA. Two-year OS was 81.9% in patients with RA and 77.8% in those without RA, with 2-year PFS of 72.6% and 72.4%, respectively. For other outcomes, HRs were <1 for patients with RA, with a statistically significant reduction in hospital admissions: 0.56 (95% CI, 0.44-0.72) in adjusted calculations. Conclusions: In conclusion, patients with RA and DLBCL did not experience worse survival outcomes or increased hospitalisation rate during therapy.