Evaluating Hip Osteoarthritis as a Risk Factor for Immune Checkpoint Inhibitor–Induced Inflammatory Arthritis

Objective To evaluate whether hip osteoarthritis (OA) is a risk factor for immune checkpoint inhibitor (ICI)-induced inflammatory arthritis (ICI-IA). Methods Patients treated for thoracic cancer with ICI therapy and with computed tomography (CT) of the abdomen/pelvis within 1 month of ICI start were included; hip OA was graded from a coronal slice of the CT by a radiologist. Chart review determined the presence of ICI-IA and other immune-related adverse events. Those with Kellgren-Lawrence grade of ≥ 2 in either hip on CT abdomen/pelvis were classified as having hip OA. Incidence rates of ICI-IA were calculated in patients with and without hip OA. Development of ICI-IA and overall survival were compared by Kaplan-Meier curves and Cox proportional hazards. Results A total of 309 patients were included; 103 had hip OA on CT scan. Overall, the cumulative incidence of ICI-IA was 54.8/1000 person-years and did not significantly differ between those with and without hip OA ( P = 0.78). In the Cox proportional hazards model, hip OA was not associated with ICI-IA development (hazard ratio [HR] 1.24, P = 0.55), but higher BMI was associated with a significantly lower hazard for ICI-IA (HR 0.93, P = 0.049). Survival did not differ by hip OA status but was improved in patients with ICI-IA (HR 0.59, P = 0.02) and higher BMI (HR 0.97, P = 0.03), and was worsened in higher cancer stage (HR 1.60, P < 0.01) in the multivariable analysis. Conclusion CT-derived hip OA was not significantly associated with development of ICI-IA in this cohort of patients with lung cancer. ICI-IA was associated with decreased mortality.