Role of Immunotherapy in Small Cell Lung Cancer, Thymic Epithelial Tumors, and Mesothelioma.

The introduction of programmed death receptor ligand-1 (PD-L1) and programmed death receptor-1 (PD-1) inhibitors into the field of non-small cell lung cancer (NSCLC) was practice changing. The pivotal trials consistently showed a clinically meaningful improvement in overall survival (OS) for patients with driver mutation-negative NSCLC, a field in which outcomes had been stagnant for decades. The success of immune checkpoint inhibitor (ICI) therapy in NSCLC has led to enthusiasm to expand the reach of these drugs into other thoracic malignancies such as thymic epithelial tumors (TETs), mesothelioma, and small cell lung cancer (SCLC). Unfortunately, the improvement in outcomes with ICI therapy in these rarer thoracic tumors has been somewhat modest, and in the case of thymoma, rates of adverse events are too high to routinely justify their use. Although the response rates seen in ICI therapy in these tumor types are similar to those seen with other available single-agent therapies for advanced disease, ICIs do present another option for clinicians treating patients with mesothelioma, small cell carcinoma, and thymic carcinoma (TC), diseases in which approved treatment options are limited. Here we review the latest trials of ICI therapy in mesothelioma, SCLC, and TETs.