Charged-particle beams consisting of protons or helium ions are a type of particulate radiation therapy that contrast with conventional electromagnetic (i.e., photon) radiation therapy due to the unique properties of minimal scatter as the particulate beams pass through the tissue, and deposition of the ionizing energy at a precise depth (i.e., the Bragg Peak). Thus radiation exposure to surrounding normal tissues is minimized. The theoretical advantages of protons and other charged-particle beams may improve outcomes but this has not been proven. At the same time proton beam radiotherapy is significantly more expensive than other modalities.1

A recent review concluded: “While there is growing enthusiasm for the use of protons in the treatment of prostate cancer, a review of the literature suggests that there is so far no clear evidence to show that proton therapy would be superior to highly conformal photon treatments. As the use of protons in prostate cancer will no doubt become more widespread in the coming years, there is urgent need for a randomized trial of IMRT vs protons to provide us with concrete clinical data about the relative merits and potential risks of each type of therapy. The possibility of launching such a trial is currently being explored by the RTOG.” 2

Until results from such a trial are available, we continue to view protons in prostate cancer as a modality with tremendous promise. As it comes with a relatively high price tag, however, proton therapy must remain under scrutiny until it has proven itself against the best possible alternative.”