Metastatic brain tumors arising from systemic cancer affect approximately 150,000 people in the United States each year (142). It is one of the most common neurologic complications of cancer, and the incidence is likely increasing with improved diagnostic techniques and more effective systemic treatments, leading to longer survival. Brain metastases have a potentially devastating effect on quality of life and patient survival. Developments in treatment of patients with brain metastases include stereotactic radiosurgery following surgical resection, molecularly targeted agents, and immunotherapy. The author of this clinical article summarizes the clinical features of brain metastases and provides an updated summary and critique of currently available treatments.
| || |
• Metastasis to the brain parenchyma is the single most frequent neurologic complication of several common neoplasms, including lung cancer, breast cancer, and melanoma.
| || |
• Brain metastases often have a devastating impact on patients' quality of life and are fatal if not controlled.
| || |
• Treatment options for patients with brain metastases include surgical resection, whole-brain radiation therapy, stereotactic radiosurgery, and in some cases chemotherapy, immunotherapy, or molecularly targeted therapy.
| || |
• The management of patients with brain metastases needs to be individualized based on the primary tumor type, number, size, and location of brain metastases, status of the systemic tumor, patients' neurologic and overall performance status, and anticipated duration of survival.
Historical note and terminology
Brain metastases are neoplasms that originate in tissues or organs outside the brain and spread to involve the brain parenchyma. Brain metastases can occur in conjunction with metastases to other parts of the central nervous system, such as the dura or leptomeninges. Metastases to the brain may be single or multiple. The phrase "single brain metastasis" refers to an apparent single cerebral lesion and makes no implication regarding the extent of cancer elsewhere in the body. The phrase "solitary brain metastasis" is used to describe the relatively rare occurrence of a single brain metastasis that is the only known site of metastatic cancer in the body. Synchronous brain metastases are present at the time of the initial systemic tumor diagnosis, whereas metachronous metastases develop later in the course of patients' disease.
Historically, patients with brain metastases had dismal outcomes, and treatment recommendations were limited to those with palliative intent. In 1926 Grant reported the first series of patients given surgical treatment for single brain metastases (67). Radiation therapy for the palliation of brain metastases was introduced in the 1950s. However, it was not until the publication of several prospective studies that demonstrated survival benefit of surgery or stereotactic radiosurgery (SRS) with whole brain radiation (WBRT) that paradigms changed (123; 122; 169). With an evolving understanding of the biology of brain metastases, as well as a more nuanced understanding of subtype specific natural histories, systemic treatment options have also had a significant impact on approaches to treatment for patients with brain metastases.