Neurological Complications Associated With Anti–Programmed Death 1 (PD-1) Antibodies

IMPORTANCE: Neurological complications are an increasingly recognized consequence of the use of anti–programmed death 1 (PD-1) antibodies in the treatment of solid-organ tumors, with an estimated frequency of 4.2%. To date, the clinical spectrum and optimum treatment approach are not established. OBJECTIVE: To investigate the frequency, clinical spectrum, and optimum treatment approach to neurological complications associated with anti–PD-1 therapy. DESIGN, SETTING, AND PARTICIPANTS: This single-center, retrospective cohort study was conducted from either September or December 2014 (the approval dates of the study drugs by the US Food and Drug Administration) to May 19, 2016. All patients receiving anti–PD-1 monoclonal antibodies were identified using the Mayo Cancer Pharmacy Database. Patients with development of neurological symptoms within 12 months of anti–PD-1 therapy were included. Patients with neurological complications directly attributable to metastatic disease or other concurrent cancer-related treatments were excluded. MAIN OUTCOMES AND MEASURES: Clinical and pathological characteristics, time to development of neurological symptoms, and modified Rankin Scale (mRS) score. RESULTS: Among 347 patients treated with anti–PD1 monoclonal antibodies (pembrolizumab or nivolumab), 10 (2.9%) developed subacute onset of neurological complications. Seven patients were receiving pembrolizumab, and 3 patients were receiving nivolumab. The patients included 8 men and 2 women. Their median age was 71 years (age range, 31-78 years). Neurological complications occurred after a median of 5.5 (range, 1-20) cycles of anti–PD-1 inhibitors. Complications included myopathy (n = 2), varied neuropathies (n = 4), cerebellar ataxia (n = 1), autoimmune retinopathy (n = 1), bilateral internuclear ophthalmoplegia (n = 1), and headache (n = 1). Peripheral neuropathies included axonal and demyelinating polyradiculoneuropathies (n = 2), length-dependent neuropathies (n = 1), and asymmetric vasculitic neuropathy (n = 1). The time to maximum symptom severity varied from 1 day to more than 3 months. The median mRS score was 2.5 (range, 1-5), indicating mild to moderate disability. Five patients experienced other systemic immune-mediated complications, including hypothyroidism (n = 3), colitis (n = 2), and hepatitis (n = 1). Treatment with anti–PD-1 antibodies was discontinued in all patients. Treatment included corticosteroids (n = 7), intravenous immunoglobulin (n = 3), and plasm