The Advanced Technology QA Center (ATC®) at Washington University in St. Louis manages secure internet transfer of images and radiation treatment planning datasets from clinical sites participating in PARTIQoL: Prostate Advanced Radiation Technologies Investigating Quality of Life; A Phase III Randomized Clinical Trial of Proton Therapy vs. IMRT for Low or Intermediate Risk Prostate Cancer. This study presents an important opportunity to examine through a multi-center randomized clinical trial (RCT) the comparative effectiveness of a promising but expensive medical technology prior to its widespread adoption and diffusion.