Rheumatic immune-related adverse effects of immune checkpoint treatment: a retrospective multicentre study

To describe the frequency, clinical spectrum, and management of rheumatic immune-related adverse events (R-irAEs) in patients receiving immune checkpoint inhibitors (ICIs) at two oncology centers in Spain. This was a retrospective, observational study involving 734 patients treated with ICIs between January 2016 and December 2022 in two Spanish hospitals. Electronic medical records were systematically reviewed to identify R-irAEs, with diagnoses confirmed by rheumatologists. The data collected included demographics, cancer type, ICI regimen, time to R-irAE onset, clinical features, management, and outcomes. Among the 734 patients, 227 (30.9%) developed any irAEs, with 54 (7.35%) presenting R-irAEs, accounting for 23.8% of all irAEs. The most common cancers were lung cancer and melanoma. Most R-irAEs occurred within six months of ICI initiation. The most frequent manifestations were polymyalgia rheumatica (n = 12) and various forms of arthritis/arthralgia (n = 26). Myositis is a particularly severe manifestation that presents at the first or second cycle of treatment. Corticosteroids are the primary treatment, with some patients requiring immunosuppressants, biologics, or intravenous immunoglobulins. Clinical improvement was observed in 88% of the treated patients, although 18 patients required ICI discontinuation due to toxicity. The increasing use of ICIs in cancer treatment is limited by development of irAEs (30.9%) and R-irAEs (7.35%) accounting for 23.8% of irAEs. Prompt recognition and multidisciplinary management, including rheumatology input, are essential to optimize patient outcomes and balance the continuation of cancer treatment. Greater awareness and standardized guidelines are needed to improve the diagnosis and care of these adverse events.