A new German study has found a modest increase in cancer risk among rheumatoid arthritis (RA) patients treated with Janus kinase inhibitors (JAKis) compared to those receiving biologic disease-modifying antirheumatic drugs (bDMARDs). The findings come from the RABBIT registry, a long-term observational cohort tracking adult RA patients in Germany.
Researchers analyzed over 6,500 treatment episodes between January 2017 and December 2020, with follow-up through June 2024. They recorded 88 malignancies in the JAKi group and 135 in the bDMARD group, excluding nonmelanoma skin cancers. Most JAKi treatments involved baricitinib or tofacitinib, while bDMARDs were primarily tumor necrosis factor (TNF) inhibitors.
The incidence rate of malignancy was 11.6 per 1,000 patient-years for JAKis and 8.9 for bDMARDs. After adjusting for confounding factors, the hazard ratio for cancer among JAKi users was 1.40, indicating a 40% increased risk.
Importantly, the elevated risk was only observed in treatment episodes longer than 16 months. Subgroups at higher risk included patients aged 60 or older, those with high disease activity, and those previously treated with three or more conventional synthetic DMARDs.
While the overall risk increase was small, the authors stressed the importance of weighing it against the known cancer risks of poorly controlled RA. They recommend personalized treatment decisions that carefully consider both disease severity and patient-specific risk factors.
These findings may inform future guidelines and shared decision-making between clinicians and patients navigating long-term RA treatment options.
Reference
Schaefer M et al. Comparative risk of incident malignancies in rheumatoid arthritis patients treated with Janus kinase inhibitors or bDMARDs: observational data from the German RABBIT register. Ann Rheum Dis. 2025:S0003-4967(25)01024-6.
