Neurosurgical management of brain metastases

Abstract

Before the 1990s, whole-brain radiation therapy (WBRT) remained the standard treatment of brain metastases (BMs). However, a seminal study by Patchell et al prospectively compared surgical resection followed by WBRT vs WBRT alone in patients with a single BM. Patients who received surgery and radiation had significantly longer overall survival, lower rates of local recurrence, and better quality of life. WBRT is rarely used as initial monotherapy for fewer than 4 BMs given the cognitive sequelae, negative effect on lifestyle, and lack of survival benefit. Therefore, surgical resection and stereotactic radiosurgery (SRS) with or without adjuvant WBRT remain the primary neurosurgical management strategies for BMs. Lesions that cause neurologic deficits, have symptomatic mass effect, or significant edema are candidates for surgical resection. Surgical resection also provides the added benefit of obtaining diagnostic tissue. Gross total resection is the goal when treating metastatic lesions. Frameless stereotaxy is often used during surgery, but a recent trial has demonstrated that frameless neuronavigation does not influence extent of resection. For lesions in eloquent locations, functional data can be incorporated into neuronavigation, namely functional magnetic resonance imaging (MRI) and diffusion tension imaging. Functional MRI can be used to localize both cortical and subcortical eloquent areas and diffusion tension imaging can aid in delineating the relationship of the lesion to important subcortical fiber tracts. Tractography can influence preoperative planning and lead to modification of the surgical approach. Advanced neuronavigation and intraoperative neuromonitoring are methods that can aid in resecting lesions in areas that were previously not considered for surgery. Focused irradiation via single-fraction SRS is another treatment of metastatic lesions that has demonstrated survival advantage in comparison with WBRT alone. Many patients present with lesions for which either surgery or SRS is an option. For solitary BM management, survival does not significantly differ between surgical resection and SRS. However, SRS is associated with lower frequency of adverse events and improved local control when compared with surgery alone. Single-fraction SRS is limited by the inability to deliver adequate dose to larger lesions. The ideal treatment modality of most larger lesions (maximum diameter 43 cm) is surgical resection. In locations that are not amenable to surgery, such as the brainstem, SRS can be