Advanced radiotherapy for metastatic disease-a major stride or a futile effort?

Radiation Oncologists are involved in patient care from cancer diagnosis to the end of life, and 30-40% of radiation courses are delivered with palliative intent. Recent data has supported the use of advanced technology in select metastatic settings with respect to improvements in symptom response, local control, and even survival. Practicing physicians must thus be aware of the appropriate uses of advanced radiation techniques, especially with the development of life-prolonging targeted therapy and immunotherapies for individuals with advanced disease. As patients live longer with metastatic burden clinicians may increasingly encounter complex clinical scenarios that strike a 'middle ground' between purely palliative or curative intent. That is, the situation in which aggressive palliation is warranted to provide durable local control and potentially improve progression free and overall survival. This article is intended to provide a framework that clinicians can utilize when considering treatment options in complex palliative settings. The review begins with an introduction to advanced radiation techniques, their relevance with respect to histology, and the importance of dosing and fractionation. It further explores the data supporting the use of advanced techniques in the setting of brain metastases, lung metastases, non-spine bone metastases, spinal bone metastases, spinal cord compression, and liver metastases. Each of the sections also discusses specific site-related factors to consider that may sway a practitioner toward or against the use of such techniques. Where applicable, outcomes of re-irradiation are also discussed.