Radiation therapy for cerebral metastases: Non-stereotactic treatment options.

Human development of the blood-brain-barrier - a semi-permeable membrane that both separates and protects the brain and spinal cord from potential toxins coursing through the human circulatory system, while simultaneously permitting oxygen and nutrient delivery - also lead to the creation of the largest sanctuary site for malignancy in the human body: the central nervous system (CNS) . The most commonly used cocktails of chemotherapeutic treatments are unable to breach the blood-brain-barrier and treat metastatic cancer cells seeking asylum behind its walls, and other sanctuary sites (e.g. genital tract, testicles, placenta and umbilical cord in pregnancy, etc.). As a result, therapies that are unobstructed by the blood-brain-barrier are of paramount importance when treating CNS metastases. Radiation therapy (RT) is among these commonly employed modalities and can be used as both a first line treatment and, in some cases, as prophylaxis against microscopic disease armed with the potential to mature into symptomatic cerebral metastases.