Long-term complete radiological response to immunotherapy in a patient with metastatic NSCLC and active rheumatoid arthritis.

The use of immune checkpoint inhibitors (ICIs) in patients with autoimmune diseases (AIDs) is challenging due to the risk of immune-related adverse events and disease flares. These patients are routinely excluded from clinical trials, leaving limited evidence to guide practice. We report a 70-year-old woman with metastatic non-small cell lung cancer (NSCLC) and active rheumatoid arthritis (RA) receiving infliximab and methotrexate. Initial treatment with platinum-based chemotherapy excluded ICIs. After disease progression, pembrolizumab was introduced with chemotherapy following multidisciplinary discussion. The patient achieved a complete radiological response without RA flare, completed two years of pembrolizumab in March 2022, and remains in remission as of August 2025. This case highlights that ICIs can be used safely in selected patients with active AID, preserving functional status and quality of life. Prospective studies in this population are needed to refine risk-benefit assessment and optimise patient selection.