Prevalence, therapy and tumour response in patients with rheumatic immune-related adverse events following immune checkpoint inhibitor therapy: a single-centre analysis

Background: Immune checkpoint inhibitors (ICIs) improved cancer therapy by inducing a higher immune system activity. This effect can cause rheumatic immune-related adverse events (rh-irAEs), which have not yet been extensively studied. Methods: We analysed 437 patients between 2014 and 2019, treated with ipilimumab (anti-CTLA-4) and/or nivolumab (anti-PD-1) or pembrolizumab (anti-PD-1) at the Clinic for Internal Medicine III, Oncology, Haematology and Rheumatology at the University Hospital Bonn, Germany. Results: Of the 437 patients 60% were males. Patients were mainly treated for melanoma, lung cancer, head and neck tumour and urothelial carcinoma. At least one immune-related adverse event (irAE) was observed in 163 patients (37.3%), including rh-irAE. Most common side effects were rash, colitis and hepatitis. We identified 19 patients (4.3%) with a minimum of one rh-irAE due to ICI therapy; three of those had a pre-existing rheumatic disease. Arthralgia developed most frequently in eight patients (42.1%). Other rh-irAEs were: arthritis ( n = 7; distinguished in rheumatoid arthritis, psoriatic arthritis, juvenile idiopathic arthritis and undifferentiated arthritis), myalgia ( n = 2) and myositis ( n = 3). Most rh-irAEs were classified as moderately severe (Common Terminology Criteria of Adverse Events grade 2: 68.4%). Median time between starting ICI therapy and the occurrence of rh-irAE was 109 days (interquartile range 40–420 days). Fifteen patients (78.9%) were treated with glucocorticosteroids. In four cases additional therapy with methotrexate or tocilizumab was required. Even though patients benefited from ICI treatment, therapy had to be discontinued in six of the participants due to rh-irAE. Interestingly, patients with rh-irAE had a significantly higher tumour response compared with patients without rh-irAE (94.4% versus 43.5%; p < 0.0001). Conclusion: Rh-irAEs occur under ICI therapy, especially in patients with higher tumour response. However, they are not the most frequent irAE after ICI exposure: 9.3% of all irAEs were rheumatic (20 rh-irAE cases in 19 patients of a total of 215 irAE cases in 163 patients)