Toi Y, et al. - Researchers performed this medical record analysis of 137 patients with advanced or recurrent non–small cell lung cancer treated with the programmed cell death protein 1 inhibitors nivolumab or pembrolizumab, to determine whether preexisting autoimmune markers, including rheumatoid factor, antinuclear antibody, antithyroglobulin, and antithyroid peroxidase, are associated with outcome or with immune-related adverse events of anti–programmed cell death 1 therapy in these patients. In addition, they sought the potential clinical biomarkers that may be meaningfully and conveniently associated with clinical benefit or with immune-related adverse events (irAEs) following anti–programmed cell death protein 1 (anti–PD-1) treatment. Findings suggest an independent and significant association of the presence of any preexisting antibody examined with immune-related adverse events and with clinical benefit. These findings suggest the possible value of detecting the presence of these autoimmune markers in ascertaining the risk-benefit ratio for these individual patients, maximizing therapeutic benefits while minimizing immune-related adverse events.