Extracranial Radiosurgery (Stereotactic Body Radiation Therapy) for Oligometastases

Extracranial radiosurgery, also known as stereotactic body radiation therapy (SBRT), is an increasingly used method of treatment of limited cancer metastases located in a variety of organs/sites including the spine, lungs, liver, and other areas in the abdomen and pelvis. The techniques used to perform SBRT were initially modeled after intracranial radiosurgery, although considerable evolution in technique and conduct has occurred for extracranial applications. Unlike intracranial radiosurgery, SBRT requires characterization and accounting for inherent organ movement including breathing motion. Potent dose hypofractionation schedules have been used with SBRT such that the treatment is generally both ablative and convenient. Because the treatment is severely damaging to tissues within and about the target, the volume of adjacent normal tissue must be strictly minimized to avoid toxic late effects. Outcomes in various sites show very high rates of local control with toxicity mostly related to tubular tissues like the airways and bowels. With proper conduct though, SBRT can be an extremely effective treatment option for oligometastases.