Introduction - Supplement on brain metastases.

As therapeutic interventions for systemic solid neoplasms continue to improve, so do median survival times and the incidence of “safe harbor” metastases. Improvements in oncologic armamentaria for the cancers that have a predilection to metastasize to the central nervous system – breast, lung, melanoma, and renal cancers – have subsequently increased the likelihood of developing brain metastases. As neurosurgeons, we are involved in delivering two of the three most common therapies for brain metastases, surgery and stereotactic radiosurgery. With the discovery of metastatic disease in the brain, a patient, by definition, has stage IV cancer. However, unlike glioblastoma, there is a significant tail to the survival curve for stage IV cancer. Although glioblastoma carries a better median survival than brain metastases (12-13 months versus 8-10 months, respectively), glioblastoma carries a much lower 5-year survival rate (less than 5% versus almost 20%). While this is important to consider when choosing among treatment options, it also leads to a difficult clinical conundrum: Should we choose treatments based on the majority of patients, or do we treat patients as though they will be long-term survivors? While this may seem prima facie obvious, every treatment carries risks as well as benefits. Complicating this issue is the fact that current standard therapies have relatively equivalent impacts (as measured by local recurrence at one year and by median survival). Furthermore, as long as brain metastases are treated, the vast majority of patients will succumb to progression of systemic disease, not to their brain metastases. Brain metastases are a harbinger of systemic disease progression. Choosing brain metastasis therapy can be straightforward. A large, solitary, posterior fossa metastasis, with secondary hydrocephalus, in a young healthy patient with controlled systemic disease and a good performance status should undergo surgical resection. A patient with miliary brain metastases, too numerous to count, is best served by whole brain radiotherapy. A patient with three asymptomatic, inoperable metastases might best be treated with stereotactic radiosurgery. Unfortunately, these clear-cut cases are the exception. Proponents of each of these treatments must temper their enthusiasm and accept the need for a multi-faceted therapeutic approach, taking into account each patient's unique way of balancing length of survival and quality of life. The overarching goal of this Surgical Neurology International Supplement is to provide the neurosurgical community with an eclectic perspective. While we must rely on our medical oncology and radiation oncology colleagues to provide systemic treatments, in order to optimize patient care for brain metastases, neurosurgeons must participate in multidisciplinary teams that make decisions driven by consensus. Multidisciplinary teams offer an improved knowledge base and a greater likelihood of evidence-based decision-making. Hopefully, this collection of reviews will provide the reader with an improved understanding of the current state of knowledge of brain metastases development, epidemiology, pathology, treatment options, controversies, and future directions.