[The CyberKnife as a perfect tool for new therapeutic challenges in radiotherapy].

The "wholy grale" in radiotherapy is the search for a treatment as conformal as possible allowing to apply very high doses on the target while leaving healthy tissues as much as possible outside the prescription isodose. Radiotherapy is characterized by a never ending technical evolution aiming at increasing biological efficacy on the target while reducing toxicity at the level of the surrounding organs at risk. One of the by-products of this ever lasting quest to precision and dose concentration is the concept of radiotherapy in stereotactic conditions. For a long time the technique has only been available for cranial non-moving targets, as high precision and moving targets have long been considered antinomic for technical reasons. The clinical need to apply these same concepts for extra-cranial locations, potentially suitable to move during the irradiations, has been a booster to develop informatics and robotics. The result of these technical developments is the CyberKnife. We intend to present this technique and highlight the experience of more than two years of clinical use in the department of radiotherapy in the University Hospital of Liège. The various indications of stereotactic radiotherapy with CyberKnife will be reviewed.