There have been five published studies investigating stereotactic boost in addition to standard fractionation EBRT without using brachytherapy, four reports with the Cyberknife platform (6-9) and one with Intensity Modulated Radiotherapy (IMRT) (10). All of these series have early follow up (FU) with reported BFFS between 77% and 100%. The largest experience is from Katz et al. (8) who reported 73 patients with both intermediate (n= 41) and high risk (n=32) disease. They treated patients with the Cyberknife platform to deliver between 18 and 21 Gy in three fractions in addition to 45 Gy in 25 fractions EBRT. With a median follow up of 33 months, BFFS was 89.5% and 77.7% for the intermediate and high risk patients respectively. A 5 mm expansion from the prostate to the Planned Treatment Volume (PTV) was used except posteriorly, where the margin was 3mm. There was 7% Grade 2 acute genitourinary (GU) and gastrointestinal (GI) toxicity, with late Grade 2 estimates at three years of 5.5% (GU) and 8.2% (GI). Three other series using Cyberknife to mimic HDR were reported between 2008 and 2012 (6, 7, 9). These studies used margins of 0-2 mm posteriorly and 3-5 mm in other directions and reported low rates of Grade 2 and Grade 3 toxicity. Two of these reports specifically attempted to reproduce the heterogeneity of HDR with large areas of the PTV receiving >125% (40% to 45%) and >150% (5% to 10%) of the prescribed dose. Miralbell et al. (10) reported a Linac based IMRT boost in 50 patients in 2010. This series used an endorectal balloon but no image guidance, which may be the cause of their unacceptably high five year estimates of late GI Grade 2 toxicity of 26%.