A certain amount of movement of the prostate normally occurs within the body. To make sure that the prostate will not be missed, a margin of tissue around the prostate also needs to be treated. Although a wide margin will ensure that the prostate is included, it will also cause more normal tissue to receive high doses of radiation. This, in turn, would result in more side effects. To reduce the margin needed around the prostate, and side effects, tiny gold seeds measuring 3.0 x 1.2mm will be inserted into the prostate which can be seen using a special type of X-Ray camera called a portal imager during treatment. This will allow for targeting of the prostate gland more precisely so that a significantly smaller margin of normal tissue will need to be treated. By using gold seeds in conjunction with SABR, there is the potential to safely deliver a more intensive dose of radiation to the prostate gland without increasing the amount of side effects.