Background/Purpose: Immune Check Point Inhibitors (ICIs) are widely used in Oncology and are associated with multiple autoimmune and systemic inflammatory reactions called immune-related adverse events. We sought to investigate the long-term outcomes of patients who develop ICI induced inflammatory arthritis (IA) and identify potential risk factors associated with IA persistence.

Methods: We conducted a retrospective chart review of patients referred to the rheumatology department for IA associated with ICIs by medical oncology between December 2015 to March 2021 at the Queen Elizabeth Hospital, Birmingham. Information was obtained using clinical records at the baseline visit and 6, 12 and 18 month follow up visits. A qualitative analysis without formal statistical testing was conducted due to the small size of the cohort.

Results: 38 patients were identified. None had pre-existing IA. There was slight male predominance (55.3% Males vs 44.7% Females). Mean age at diagnosis was 65.2 years. Mean Duration of IA was 15.2 months. The knee was the most commonly involved joint (84.2%) at Baseline. Mean baseline CRP was 63.3 mg/L. All patients were ACPA negative, 2 had borderline RF positivity. Mean interval between the first immune checkpoint inhibitor infusion and the onset of the rheumatic adverse events was 6.4 months. ICIs were stopped in 11/38 (28.9%) and temporarily suspended in 5/38 (13.2%) due to IAs. 18/28 (47.3%) required DMARDs and 4/38 (10.5%) were initiated on tumour necrosis factor alpha inhibitors. Persistence at follow up was defined as the presence of clinically assessed synovial swelling and/or ongoing requirement for corticosteroid or DMARD treatment for IA. At 6, 12 and 18 months follow up, 27/34 (79.4%), 16/24 (66.7 %) and 13/23 (56.5%) of patients had persistent IA respectively. Persistence at 6 months follow up was associated with non-smoking status in 18/18 patients (100%), additive course (defined as patients who develop more inflamed joints in addition to the primarily affected joint) in 23/24 patients (95.8 %) and ANA positivity in 19/20 patients (95%). In comparison, all non-persistors had a history of smoking; only one patient had an additive course: 1/24 (4.2%) and only one patient had ANA positivity: 1/20 (5%) in this group. IA was more likely to persist in patients who presented with baseline characteristics such as insidious onset, polyarthritis, symmetrical pattern and, involvement of both small and large joints. Patients with persistent IA had more flares in first six months as compared to non-persistors. Non-persistors had a numerically slightly higher total corticosteroid exposure over the first three months as compared to persistors.

Conclusion: Our findings highlight that ICI-induced IA can become a long term complex disease necessitating management by rheumatology for immunosuppression. Large multicentre cohorts are required to confirm potential risk factors for persistence versus remission.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/potential-predictors-of-persistence-in-immune-check-point-inhibitor-induced-arthritis/