**1. Introduction**

Among all malignancies, lung cancer showed the highest reported incidence and mortality in 2018 [1]. The prognosis of advanced and recurrent lung cancer is poor, and standard treatments with cytotoxic anticancer drugs have limited therapeutic effects. Recently, with the development of molecularly targeted drugs based on the results of genetic testing and immunotherapies for cancer, treatments for non-small cell lung cancer have undergone remarkable development. Molecularly targeted drugs for cancer can differentiate between cancer cells and normal cells at the genome and molecule levels and act by specifically suppressing the molecules required for cancer growth and metastasis. Cytotoxic drugs are different as they have defined molecular targets from the stage of drug discovery and therapy design, and their targets are often biomarkers, especially those predicted for treatment. In non-small cell lung cancer (NSCLC), driver oncogene mutations, which confer advantages to the growth and viability of cancer cells, are the mainstay of biomarkers. EGFR gene mutations, ALK gene translocations, ROS1 gene translocations, and BRAF gene mutations have been used, and tyrosine kinase inhibitors targeting these aberrations have elicited high response rates.

Since around 1970, immunotherapy has been initiated for lung cancer with nonspecific treatments such as OK-432, and has progressed to specific immunotherapies such as peptide vaccine therapy. However, no treatment has shown apparent efficacy beyond the standard of care with cytotoxic anticancer drugs. In recent years, as the detailed mechanism of tumor immunotherapy is understood, and anti PD-1 antibodies, one of the immune checkpoint inhibitors, have shown good results in
