Immune checkpoint inhibitor rechallenge in patients who previously experienced immune-related inflammatory arthritis: a multicentre observational study

Objective Another course of immune checkpoint inhibitors (ICIs) is often considered in patients with cancer progression and previous immune-related adverse events, including inflammatory arthritis (ICI-IA), but there are limited data regarding safety of ICI rechallenge in this setting. We aimed to assess the rate and clinical features associated with ICI-IA flare/recurrence on ICI rechallenge.Methods We conducted a multicentre observational study including cancer patients with ICI-IA who started a second course of ICI more than 3 months after ICI discontinuation in four French university hospitals. Primary outcome was the frequency of ICI flare/recurrence after ICI rechallenge.Results Twenty-three patients were included. At the time of ICI rechallenge, 18 patients reported no symptoms of ICI-IA (78%) and 5 had grade 1 (22%), 11 patients (48%) were not receiving any ICI-IA treatment, 11 (48%) were still on prednisone, 2 (9%) were on conventional synthetic disease-modifying antirheumatic drugs and 1 (4%) on anti-IL-6. ICI-IA flare/recurrence occurred in 12 patients (52%) with a median time of 1 month after ICI rechallenge. ICI-IA phenotype, disease activity and ICI-IA treatment at the time of ICI rechallenge did not differ according to ICI-IA flare/recurrence status.Conclusion In this first observational study of ICI-IA patients rechallenged with ICI, about half of the patients experienced ICI-IA flare/recurrence with a similar phenotype but occurring earlier than the initial ICI-IA, warranting close monitoring during the first month of retreatment. Risk of flare did not differ according to baseline immunosuppressive treatment at the time of rechallenge.