An Update on Current and Emerging Therapies for Brain Metastases

Abstract

Brain metastases (BMs) are the most common cause of brain malignancy, occurring 10 times more often than intracranial neoplasms. BMs most frequently arise from non-small cell lung cancer, melanoma, renal cell carcinoma and breast carcinoma. The overall survival after BM diagnosis remains poor, but depends on patient age, performance status, type of primary tumour, time of diagnosis from the primary, as well as many other factors. The incidence of BMs may be due to the fact that some therapies control growth of the primary tumour, but such agents has a limited role in BM treatment, as they cannot or only partially penetrate the BBB. The brain therefore acts as a ‘sanctuary site’ for cancers which have successfully invaded the brain and escaped the effects of systemic cancer therapies. A reduced effect of classical systemic therapies on BMs can also be explained by other resistance mechanisms that only occur in the brain such as the astrocytic protection of extravagated cancer cells. Alternative approaches include surgery, stereotactic radiosurgery or whole brain radiotherapy. This review looks at the benefits and risks of different approaches to treatment of BMs and highlights areas of research in both current and prospective BM therapies.