Is proton beam radiation effective in treating prostate cancer?
Proton beam therapy is a type of external beam radiotherapy that works by aiming energetic ionizing particles (in this case, protons accelerated with a particle accelerator) onto the target tumor. Because protons are relatively large, they do not spread or “scatter” significantly in tissue. Therefore, the beam stays focused on the tumor, with less radiation delivered to surrounding structures. It is possible to focus the proton beam at the precise depth in the tissue where the tumor is situated. Proton therapy has been used for numerous tumors throughout the body, including the prostate. Some studies in prostate cancer show a reduction in long-term rectal and genitiourinary side effects when compared with conventional X-ray therapy. However, other studies show that the difference is small and limited to a small subset of cases where the prostate is particularly close to certain anatomical structures (Slater JD et al. Int. J. Radiat. Oncol. Biol. Phys. 59: 348-352 (2004); Zietman AL et
