Dose Escalation Using Fiducial Markers in Image Guided Volumetric Modulated Arc Therapy to the Focal Lesion Micro Boost of Localized Prostate Cancer

Gold markers implanted in the prostate are used frequently for position verification of the prostate during external-beam radiotherapy. By using the markers as a surrogate for the prostate itself, not only set-up errors, but also the internal motion of the prostate relative to the bony anatomy can be identified. It is thus believed that escalated dose marker guided radiotherapy should result in better biochemical control compared to conventional external beam radiotherapy, with a similar or lower incidence of toxicity. However, clinical data to support this is still limited. The purpose of this study is to directly compare late toxicity as well as biochemical control between patients treated with dose escalated marker guided radiotherapy versus conventional dose non-marker guided radiotherapy who has otherwise been treated with similar radiotherapy planning techniques and equipment. Prostate magnetic resonance imaging has undergone several technical improvements and shows promises for prostate tumor detection and localization. In addition to morphological information, magnetic resonance imaging allows an estimation of physiological properties of tissues. Diffusion-weighted magnetic resonance imaging is sensitive to restriction of diffusion of water molecules, and dynamic contrast enhanced magnetic resonance imaging can analyze tissue micro vascular properties. Multi para metric magnetic resonance imaging combining Diffusion-weighted and Dynamic contrast enhanced has demonstrated its value in distinguishing malignant from benign prostate tissue. Higher radiation dose levels were consistently associated with improved biochemical control outcomes and reduction in distant metastases. Radiation dose was one of the important predictors of long-term biochemical tumor control. Dose levels \< 70.2 Grey and 70.2-79.2 Grey were associated with 2.3 and 1.3-fold increased risks of pro static specific antigen relapse compared with higher doses. However, further dose escalation