According to the Central Brain Tumor Registry of the United States (CBTRUS), the incidence rate of all primary malignant and non-malignant brain and central nervous system tumors (CNS) for 2005 to 2009 was 20.6 cases per 100,00 (7.3 per 100,000 for malignant tumors and 13.3 per 100,000 for non-malignant tumors) (Fig. 1) .
Figure 1. Average annual incidence rates of primary brain and CNS tumors by age and type of tumor .
The incidence rate for children between 0 and 19 years old was 5.13 per 100,000. For adults over 20 years of age, the incidence rate was 26.8 per 100,000. The rate was higher in females (22.3 per 100,000) than males (18.8 per 100,000).
The distribution of the type of brain and CNS tumors is shown in Figure 2.
Figure 2. Distribution of brain and CNS tumors by type .
Non-malignant meningioma was most frequently reported as it accounts for more than a third of all tumors. Glioblastoma was the second most frequent type to be reported followed by tumors of the pituitary.
Brain metastases are a common complication of cancer. The incidence of brain metastases is increasing worldwide . About 160,000 to 170,000 of new cases occur per year in the United States. The most frequent types of cancers that tend to develop brain metastases are lung cancer, breast cancer, and melanoma, which account for 67%-80% of all cancers . The most recent population-based study was conducted by Barnholtz-Sloan et al.  who used the Metropolitan Detroit Cancer Surveillance System and found the incidence percentage of brain metastases to be 9.6% between 1973 and 2001. Overall, population-based studies show incidence rates of brain metastases ranging from 8.3 to 14.3 per 100,000 population and 8.5-9.6% among cancer patients. However, the majority of these studies predate the utilization of advanced imaging techniques for diagnostics and new chemotherapies for treatment of systematic cancers, which may prevent the development of brain metastases. Advances in imaging and treatment modalities, increased survival times of patients, and a relative increase in cancer incidence as the population ages may contribute to the increase in lesions diagnosed.
2. Current Standard of Care
Despite advances in care, the prognosis of patients suffering from brain metastases is still poor, and both quality of life and life expectancy is considerably reduced. Imaging and computer technologies, especially radiotherapy for treatment of brain metastases has developed greatly over the past decades . Whole-Brain-Radiation-Therapy (WBRT) and steroid therapy has been the standard of care. Untreated patients have a median survival of about four weeks . WBRT increases the median survival time to three to six months. However, WBRT involves irradiation of healthy brain tissue, which results in side effects, such as neurotoxicity, hair loss, skin irritation, nausea, vomiting, and in rare cases, leukoencephalopathy and radiation necrosis...