Toi Y, et al. - In this medical record analysis, researchers evaluated the safety and effectiveness of anti-programmed cell death protein 1 (anti–PD-1) treatment in patients with subclinical disease with advanced non–small cell lung cancer (NSCLC) and with or without preexisting autoimmune markers, including rheumatoid factor, antinuclear antibody, antithyroglobulin, and antithyroid peroxidase, as well as assessed potential clinical biomarkers that may be meaningfully and conveniently correlated with clinical benefit or with immune-related adverse events (irAEs) following anti–PD-1 treatment. Between January 2016 and January 2018, 137 patients were retrospectively evaluated who received nivolumab or pembrolizumab monotherapy at Sendai Kousei Hospital in Japan. In patients with NSCLC treated with nivolumab or pembrolizumab, the presence of the examined preexisting antibodies was related to clinical benefit and with the development of irAEs. The presence of these autoimmune markers can, therefore, help to determine the risk-benefit ratio for individual NSCLC patients, maximizing therapeutic benefits while minimizing irAEs. Findings revealed that skin reactions were more common in patients with preexisting rheumatoid factor, while thyroid dysfunction was more common in patients with preexisting antithyroid antibodies.