Radiotherapy for brain metastases: are we getting better?
Brain metastases are the most common malignant adult CNS tumor. The blood brain barrier (BBB) prevents many drugs from achieving therapeutic concentrations in the central nervous system (CNS), leaving the brain as a potential sanctuary site of disease and underscoring the importance of radiotherapy. Neurons, glial cells and vascular endothelium are prone to radiation-induced damage. Efforts have been made to reduce radiation-induced toxicity and increase efficacy (Stereotactic radio-surgery - SRS, advanced radiation-techniques that allow decreasing the dose to the hippocampi, while intensifying the radiation dose to large brain metastases or administering neuroprotective or radiation sensitizing agents during whole brain radiotherapy -WBRT in order to increase the therapeutic ratio). Surgery, radiotherapy and new pharmacological agents may become advantages for specific patient subgroups or in specific disease stages. Choosing how to treat brain metastases, must take into consideration patients and disease parameters (the primary tumor, age and performance status, systemic and brain tumor burden), and the potential risks and benefits of a treatment tool emphasising QOL considerations. Which modality to apply and when, is often a matter of local practice and treatment availability since level I evidence is lacking. The technology behind WBRT, FSR and SRS has substantially advanced over the previous decade, however only formal clinical trials will allow a definite answer to the question - are we getting better?