Musculoskeletal rheumatic complications of immune checkpoint inhibitor therapy: A single center experience.

Background: The use of immune checkpoint inhibition (ICI) has revolutionized cancer treatment. However, these medications are associated with significant and potentially debilitating immune-related adverse events (irAEs). While certain toxicities have been well studied, rheumatic complications have been less widely recognized and characterized.

Methods: We report our experience of patients who were evaluated by rheumatology after the development of a suspected rheumatic irAE following ICI treatment. Cases of rheumatic irAEs were included if active rheumatic signs or symptoms developed during or after ICI treatment and were confirmed by a treating rheumatologist.

Results: Twenty-nine patients were evaluated by rheumatology for suspected rheumatic irAEs. Eighteen patients had confirmed toxicity including inflammatory arthritis (n = 12) and PMR (n = 6). Twelve patients had de novo toxicity and six had a flare of a pre-existing rheumatic condition. The onset of de novo toxicity occurred late into treatment (median 38 weeks), while patients with pre-existing rheumatic disease flared soon after initiation of ICI treatment (median 4.6 weeks). Management often required systemic or intra-articular steroids, with initiation of disease modifying anti-rheumatic drug (DMARD) therapy in those unable to wean off steroids.

Conclusion: De novo rheumatic irAEs are generally delayed in onset after ICI initiation, while flares of pre-existing rheumatic conditions occur shortly after ICI initiation. Effective management often requires systemic corticosteroids as well as DMARDs in a subset of patients. Future prospective studies are needed to accurately describe the incidence and spectrum of rheumatic irAEs and to identify the most effective management strategies.