Prostate cancer is the most common cancer in men and the most common cause of cancer death in older men. Alternative to radical prostatectomy, radiotherapy is an important curative treatment option with comparable long-term tumour control. A recently published comparative analysis including more than 50,000 patients found a superiority of radiation therapy in comparison to radical prostatectomy in all defined risk groups. This book presents an overview of many innovative techniques that have been introduced for prostate cancer radiotherapy. Technological advances in the recent years include imaging techniques for prostate cancer detection, including magnetic resonance imaging, positron emission tomography and transrectal ultrasound. Imaging techniques are increasingly used for target visualization before or even during radiotherapy. However, the most important consequence of these advances is a safe application of a high and efficient dose that is tolerated well by our patients. An easily injectable hydrogel spacer has been developed to increase the distance between the prostate and anterior rectal wall. Thus, the rectal wall can be excluded completely from the planning target volume without the risk of missing the prostate cancer for the first time in external beam radiotherapy.