Rheumatic immune-related adverse events in patients on anti-PD-1 inhibitors: Fasciitis with myositis syndrome as a new complication of immunotherapy.

OBJECTIVE: To evaluate the prevalence and type of rheumatic immune-related adverse events (IRAEs) in patients receiving programmed cell death protein-1 (PD-1) inhibitors. METHODS: This is a single-center prospective observational study, including all cancer patients receiving PD-1 inhibitors between January 2016 and January 2018. RESULTS: During the period analyzed, we evaluated a total of 11 patients. No patient had pre-existing rheumatic or autoimmune disease. In this period, a total of 220 patients were treated with PD1 inhibitors in our center; therefore, the estimated minimum prevalence of rheumatic IRAEs related to these therapies in our population was 5%. The rheumatic IRAEs evaluated included 5 cases of oligo- or polyarthritis, 1 with a polymialgia rheumatica-type syndrome, 2 cases of immunotherapy-induced sicca syndrome, 2 patients who presented symptomatic inflammatory myositis with fasciitis in lower extremities, and 1 patient with a paraneoplastic acral vascular syndrome. The median time to IRAE after anti-PD1 exposure was 8 weeks (range: 2-24). In 5 patients, immunotherapy was discontinued (due to the adverse effect in three and cancer progression in two). In general terms the symptoms resolved completely with symptomatic treatment. Disease-modifying antirheumatic drugs were needed for 2 patients. CONCLUSION: Rheumatic IRAEs should be kept in mind during the follow-up and evaluation of patients treated with PD-1 inhibitors. The concomitant development of symptomatic inflammatory myositis with fasciitis in lower extremities appears to be a new adverse effect of anti-PD-1 immunotherapy. Additional studies are needed to determine how to adequately control and manage these complications.