Baseline predictors of disease severity in immune checkpoint inhibitor-induced inflammatory arthritis.

OBJECTIVES: To determine baseline risk factors for requiring immunosuppression and having persistent arthritis in patients with immune checkpoint inhibitor-induced inflammatory arthritis (ICI-IA). METHODS: Participants were adults with rheumatologist diagnosed ICI-IA. The primary outcome was requirement of conventional synthetic (cs) or biologic (b) DMARDs; other outcomes were persistence of IA > 6 months after ICI cessation and requirement of corticosteroids. Logistic regression models evaluated associations between clinical features and primary and secondary outcomes, with adjustment for potential confounders, as appropriate. RESULTS: 126 patients with ICI-IA were included; 53 patients (42%) required a csDMARD/bDMARD. In univariate logistic regressions, higher CDAI, tenosynovitis, longer symptom duration before first rheumatology visit, and longer ICI duration were significantly associated with a higher likelihood of requiring DMARDs; there was a trend toward those treated with prior chemotherapy being less likely to need DMARDs. After adjustment, tenosynovitis, longer symptom duration, and higher CDAI remained associated with requiring DMARDs, while those with prior chemotherapy were significantly less likely to require DMARDs. Combination anti-CTLA-4/PD-1 therapy and steroid use at baseline were associated with a higher risk of persistent IA. CONCLUSION: Higher levels of disease activity, tenosynovitis, and longer symptom duration prior to rheumatology referral were associated with requiring DMARDs for ICI-IA, while those treated previously with chemotherapy were less likely to require additional immunosuppression. The presence of risk factors for severe disease at baseline may indicate a role for higher initial steroid dose, earlier rheumatology referral, and adoption of immunosuppression beyond steroids to improve outcomes.