Metastatic Primary Lung Cancer

The three most common solid organ sites of primary lung cancer metastasis are bone, brain, and the adrenal gland. When metastasis occurs, the patient is considered stage IVA if there is a single site of metastasis (M1b) or stage IVB if multisite metastasis (M1c). Historically, there were no treatment options available for curative intent. Currently, there are treatment options that lead to increased survival, prolonged remission, and in few select cases potential cure. The progression of molecular testing and next-generation sequencing now identifies specific oncogenic driver mutations that provide targeted therapy options with therapeutic drugs. In addition, the introduction of immunotherapy, such as check point inhibitors, provides additional opportunities for treatment. Continued expansion of our understanding of molecular pathways, immunotherapy targets, drug development, and selective use of stereotactic body radiotherapy (SBRT) have provided some patients with stage IV lung cancer prolonged survival and improved treatment options.