Metastatic brain tumors (MBT) are the most common tumor type encountered in the brain. As survival of patients with primary tumors has improved over time, the incidence of MBT has increased. In this chapter, the basic biological and clinical aspects of metastatic spread to the brain are presented, including an overview of the epidemiology of MBT and recent advances in tumor biology particularly relevant to brain metastasis. Therapeutic strategies for MBT, including surgery, radiation, and chemotherapy, are reviewed, with an emphasis on application of randomized clinical trial data to practice guidelines. Finally, systemic metastases of primary brain tumors are discussed. Although relatively rare in comparison to metastases of systemic cancers to the brain, the frequency of extraneural metastases is increasing as therapy for primary brain tumors improves, thus warranting consideration.

INTRACRANIAL METASTASES

Epidemiology

Brain metastases are the most common intracranial tumor seen in adults, with approximately 10 percent of adults with cancer developing symptomatic brain metastases [1]. In the United States, the estimated prevalence of brain metastases is 200,000 cases per year [2], with an incidence of 8.2 per 100,000 persons [3]. The three most common primary cancers that metastasize to the brain are lung (38%), breast (19%), and melanoma (13%). Among these, melanoma demonstrates the highest likelihood of metastasis, with a rate approaching 50 percent in patients diagnosed with the disease.