Eligible patients are those who receive reimbursed immunotherapy or cytotoxic chemotherapy after failure of platinum-based chemotherapy per current health insurance reimbursement criteria. This study will not provide any additional intervention to patients, but they will receive all treatments available per standard of care at each institution. If the reimbursement criteria change or expand (to include the immunotherapy as the first-line therapy) in the future, patients who get to receive immunotherapy or cytotoxic chemotherapy according to the revised and expanded reimbursement criteria will be enrolled as well.~Because immunotherapy was superior to the existing cytotoxic chemotherapy in terms of survival and AEs in previous large-scale prospective studies, immunotherapy has been preferred than cytotoxic chemotherapy after failure of platinum-based chemotherapy in real-world clinical settings. In addition, pembrolizumab and nivolumab are reimbursed according to PD-L1 expression levels, but atezolizumab is reimbursed for all patients regardless of PD-L1 expression levels and thus is available for reimbursed prescription for practically every patient. These three agents showed almost no difference in their clinical effectiveness in previous prospective global studies. However, cytotoxic chemotherapy is selected over immunotherapy in some patients, and they will be assigned to the control group.~Based on the patient's symptoms and the physician's clinical judgment, cytotoxic therapy can be selected as a second-line therapy in clinical settings if the patient has an extensive lesion that requires inducing a rapid response or has experienced a disease progression centered on bone or liver metastases, which are known to respond only marginally to immunotherapy.
The prospective non-randomized case-control study to elucidate optimal target population of immunotherapy from real-world lung cancer patients