ML-13 Primary central nervous system malignant lymphoma in a patient with rheumatoid arthritis receiving tocilizumab

Background: Although the risk of developing malignant lymphoma is higher in patients with rheumatoid arthritis (RA) than in the general population, the occurrence of primary central nervous system lymphoma (PCNSL) in patients with RA is extremely rare. In recent years, there has been concern that biological disease-modifying antirheumatic drugs (DMRADs), which are widely administered to patients with RA, may increase the risk of developing cancer. We report the first case of PCNSL in a patient with RA who was treated with the biological DMRADs, tocilizumab. Case description: A 70-year-old man, who was diagnosed with RA in 2010 was treated with low-dose methotrexate from 2010 to 2015. He was started on tocilizumab in 2012. In 2018, he suffered from gait disturbance and was diagnosed with lumbar spinal stenosis. He underwent L2/3 posterior fusion surgery, but his paraplegia gradually deteriorated. Two months after the surgery, a head Gd-MRI showed multiple contrast-enhanced lesions in the basal ganglia and brain stem. A stereotactic brain biopsy was performed and DLBCL was diagnosed, and finally PCNSL was diagnosed because of no neoplastic lesions in other organs. He was treated with 5 courses of MTX 3.5g/m2 with rituximab and has been in remission for 23 months. He has maintained an independent life with residual paraplegia, but his ADLs gradually worsened. He was restarted on tocilizumab with a diagnosis of worsening RA. Conclusion: Low-dose methotrexate and biological DMRADs including tocilizumab, have been concerned to increase the risk of cancer in patients with RA, but there is no solid evidence. Since it has been a short time since the use of biological DMRADs, further accumulation of cases and careful follow-up are necessary.