Long-lasting responses after discontinuation of nivolumab treatment for reasons other than tumor progression in patients with previously treated,advanced non-small cell lung cancer

Dear Editor,Nivolumab,an inhibitor of programmed cell death 1(PD-1),is an immune checkpoint inhibitor(ICI)that enhances T cell functions by preventing negative regulation of cancer immunity,and it has shown clinically significant efficacy and tolerability in various types of cancer.Based on the results of randomized phase III trials comparing nivolumab with docetaxel[1,2],nivolumab is now used in clinical practice for patients with previously treated advanced non-small cell lung cancer(NSCLC).Fur-thermore,the most recent Japan Lung Cancer Society guidelines include nivolumab monotherapy in the sys-temic treatment strategy for previously treated,locally advanced or metastatic NSCLC[3].However,ICIs induce characteristic immune-related adverse events(irAEs),which are not seen with conventional cytotoxic agents or molecular targeted agents.IrAEs can occur in any organ system,most typically the skin,lung,and gastrointesti-nal,hepatic,and endocrine systems.