Lung cancer is the most common cause of cancer mortality worldwide, accounting for 25% of all cancer deaths with an incidence rate of 1.2 million people per year. The main risk factor of lung cancer is smoking; the risk of lung cancer is tenfold higher in smokers than in non-smokers. Lung cancer can typically be grouped into two large categories: small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), which account for 15% and 85% of lung cancers, respectively. The discovery of cancer biomarkers, specific molecules that help to distinguish between normal and cancerous conditions, may potentially be used to develop a more effective diagnostic tool for lung cancer. Cancer biomarkers consist of either of genetic materials or proteins because cancer is a heterogeneous disease that reflects gene and protein changes within a cancer cell. However, proteins are the main functional units of biological processes. Almost all of the Food and Drug Administration (FDA)-approved cancer biomarkers are protein markers. Proteomics is a powerful tool for identifying lung cancer biomarkers that can be tested in the blood. Previously, our group reported several potential lung cancer biomarkers, including plasma kallikrein (KLKB1) protein fragments, serum amyloid A (SAA), haptoglobin Î² chain [Hp Î²], and complement component 9 (C9), using proteomics approaches.