Pos0715 Treatment Patterns of Immune Checkpoint Inhibitor (Ici) Induced Arthritis and PMR at the Rheumatology Clinic at Karolinska University Hospital Between 2020 and 2023

Background: The best treatment strategy for the treatment of rheumatological immune-related adverse events (r-irAEs) induced by cancer immunotherapy with immune-checkpoint inhibitors (ICIs) is yet to be established. The current guidelines recommend glucocorticoids (GCs) as a first line treatment, while conventional synthetic disease modifying anti-rheumatic drugs (csDMARDs) and biologic DMARDs (bDMARDs) are recommended only after inadequate effectiveness of GCs. Objectives: To assess the effectiveness of GCs therapy as a first line treatment and the need of treatment escalation with a DMARD and its effectiveness in patients developing two of the most common rheumatic irAEs, arthritis with or without polymyalgia rheumatica (ir-A +/-PMR) or PMR alone (ir-PMR). Methods: We retrospectively analyzed 42 patients who were diagnosed with ICI induced ir-A +/-PMR or ir-PMR only after referral to the rheumatology department at Karolinska University Hospital from the oncology department between Jan 2020 and Dec 2023. Demographics, clinical and treatment data regarding both cancer and the r-irAE were collected according to a predefined dataset. Clinical assessment of the irAE activity at baseline, 3, 6 and 12 months was performed and defined by the treating rheumatologist as remission, low, medium or high disease activity. We even assessed the percentage of patients that were GCs free at 3, 6 and 12 months. Results: In Table 1 the baseline characteristics of the patients in the cohort are summarized. Almost all patients received GCs as a first line treatment. The median dose of prednisolone was 10 mg per day. Of the ir-A +/-PMR group 46% received a second line treatment with either a csDMARD or a biologic while none of those med ir-PMR only like symptoms needed treatment escalation. 15% of the ir-A +/-PMR needed treatment escalation with a third line treatment either with a csDMARD or a biologic and none of the PMR group. The irAE activity assessed by the treating rheumatologist at baseline at 3, 6, 12 months was calculated för the 2 groups (Figure 1). We found that only 12.5 % of the ir-A +/-PMR were cortisone free at 3 months, 37 % at 6 months while 65.4% are cortisone free at 12 months. In contrast, 22% of the ir-PMR group were cortisone free at 3 months, 75% were cortisone free at 6 months, 87.5% at 12 months. At 3 months 40.6% of the ir-A+/-PMR and 62,5% of the ir-PMR group were in remission, at 6 months 53.8% of the ir-A +/-PMR group and 87,5 % of the ir-PMR group and. at 12 months no disease activity was found at 60% of the ir-A +/-PMR grupp and at 87,5% of the PMR group. Conclusion: In this cohort, almost half of patient developing arthritis after start of ICI treatment respond inadequately to GC alone and need treatment escalation with start of a csDMARDs and even a bDMARD. Almost all patients achieve low disease activity or remission. Patients developing a PMR like syndrome respond adequately to GCs alone. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: None declared.