Prevalence and outcome of steroid-resistant/refractory pneumonitis induced by immune checkpoint inhibitors

Background: Anticancer immune-checkpoint inhibitors (ICI) can cause immune-related adverse events (irAEs), including interstitial pneumonitis, which is managed chiefly with systemic corticosteroids. When corticosteroids fail, second-line immunosuppressive therapy is indicated. Our objective was to evaluate the prevalence and outcomes of ICI-induced pneumonitis requiring second-line immunosuppressive therapy (IS). Methods: We collected data form the REISAMIC pharmacovigilance registry and the multidisciplinary immunological toxicity board at Gustave Roussy (France). No response to steroids was called steroid-refractory pneumonitis and relapse after an initial response was defined as steroid-resistant pneumonitis. Results: Of the 1187 patients screened from the REISAMIC register, 48 (4%) patients had pneumonitis treated with corticosteroids. Five of them (10%) had corticosteroid refractory/resistant disease but only 2 were treated with immunosuppressive therapy. Four additional patients requiring immunosuppressive therapy identified via the immunological toxicity board were included. Immunosuppressive therapy were cyclophosphamide (n=4 pts), infliximab (n=1 pt), intravenous immunoglobulins (n=1 pt). Five of these six patients had corticosteroid-refractory disease and one had corticosteroid-resistant pneumonitis. Five patients had severe pneumonitis (Common Terminology Criteria for Adverse Events grade ≥3) at initial pneumonitis diagnosis. Two months mortality rate in patients treated with IS was 67% (4/6). Among the patients treated with IS, the two patients alive at 5 months were treated with cyclophosphamide. Conclusion: Patients with ICI-pneumonitis treated by steroids received IS in 10% of cases. High mortality at 67% of patients was observed in ICI-pneumonitis after steroid failure. Cyclophosphamide could be a treatment option for pneumonitis after corticosteroid failure that requires further investigations.