Checkpoint inhibitor-induced rheumatological adverse events: real-world experience from northeast england

Abstract Background/Aims Immune checkpoint inhibitors (CPIs), in the form of either single agent anti-PD1 or combination therapy with anti-PD1/anti-CTLA4 monoclonal antibodies, are widely used in clinical practice. Whilst CPI-induced rheumatological immune-related adverse events (RirAEs) are relatively infrequent compared to other toxicities (8-12%), increasing CPI use in oncology settings means a growing number of patients are affected. As part of an audit of inter-specialty referrals, we evaluated patients developing new musculoskeletal symptoms on CPI treatment and the breadth of specialist-confirmed RirAEs. Methods Two sources of data were reviewed. First, consecutive consultant-confirmed RirAE cases in our rheumatological service between 2017 and 2022 (referred to as the ‘RirAE cohort’) were evaluated. Second, an observational cohort of 50 consecutive oncology patients treated with CPIs from 2019-2022 in whom symptom questionnaires had been completed (“Oncology cohort”) was reviewed. Local audit registration/safeguarding approvals were obtained. Medical records were reviewed by two medical professionals, and anonymised data analysed in a spreadsheet. Results 24 patients were identified in the RirAE cohort, of whom most presented with arthritis (Table 1). Amongst 50 patients in the Oncology cohort, 20 (40%) reported new-onset/worsening musculoskeletal symptoms on a questionnaire (“MSK-symptomatic Oncology Cohort”). Three of these were referred, diagnosed and counted amongst the RirAE cohort. Of the remaining 17, 6 were identified as having developed musculoskeletal pain by consulting oncologists; the remaining 11 were not objectively identified as having experienced potential musculoskeletal toxicity (Table 1). Conclusion Confirmed RirAEs comprised predominately seronegative, oligoarticular presentations with notable PMR overlap. In the oncology setting, the self-reported joint symptoms of 20/50 (40%) patients were identified by a physician and 3/9 of these (33%) were referred for a specialist opinion. RirAEs may be more common than appreciated amongst CPI recipients, and the extent of low-grade inflammatory arthritis unreported or “hidden” amongst other irAEs is not clear. Early evaluation of new-onset musculoskeletal symptoms in CPI recipients, and close cross-specialty collaboration, could reduce morbidity for patients who already face significant health challenges. Disclosure A. Gault: None. K. Williams: None. C. Stewart: None. A.E. Anderson: None. R. Plummer: None. A.G. Pratt: None.