AbstractID: 9826 Title: Introduction to Extracranial Stereotactic Radiosurgery: II. Clinical Experience The spatial accuracy, conformality, and high dose gradients of stereotactic radiosurgery are characteristics which make it well suited for use in treating a variety of extracranial targets. In particular, use of extracranial stereotactic radiosurgery (ESR) may be advantageous in any clinical situation in which a dose-response relationship for a welldefined tumor coexists with surrounding dose-limiting normal tissues. Given that lung and liver are some of the more challenging locations for achieving spatial accuracy with conventional treatments, tumors within these locations dominate current clinical experience, although ESR has been used in multiple other organ systems. Published early results demonstrate excellent response rates and remarkably low toxicity using a variety of hypofractionated dose regimens and a variety of localization and immobilization techniques. This portion of the course will provide an overview of the variety of clinical situations in which ESR has been used along with a description of some methods used for dose selection. Emphasis will be placed on improvements in clinically relevant patient outcomes which are potentially achievable with this exciting new modality.