Significance of Immune Checkpoints in Lung Cancer

Lung cancer is the second most common cancer in both men and women and is associated with the highest number of cancer-related deaths among all cancer diagnoses. The major types of lung cancer include non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). Systemic therapy is part of treatment for patients with earlier-stage NSCLC, when the goal is to cure, and in patients with later stage, where the goal is to prevent cancer-related complications. In addition to chemotherapy and targeted therapy, systemic therapy also includes immunotherapy in the form of immune checkpoint inhibitors. These drugs block either PD-1, PD-L1, or CTLA4 and are used either alone or in combination with chemotherapy. Inhibitors of PD-L1 also improve outcomes for patients with extensive stage SCLC, where the goal of treatment is palliation. Their use in patients with limited stage SCLC, where the goal of treatment is cure, is currently being explored. PD-L1 expression and tumor mutation burden are generally predictive of benefit from immunotherapy in NSCLC but not in SCLC. There is active ongoing research for additional immunotherapy targets and biomarkers to better select patients with lung cancer who might benefit from immunotherapy agents.