Proton therapy

Proton therapy, also referred to as proton-beam therapy, is the most common type of particle therapy. It represents one of the highly conformal radiation therapy techniques that, differing from the other external-beam photon therapies, uses the proton particle properties to minimize the toxic effects over normal surrounding tissues.

The advantage of proton therapy is the reduction in beam entry and exit dose due to the physical properties of the Bragg peak. This allows higher dose gradients to be delivered and thus can increase tumor dose while reducing dose to adjacent organs at risk (OARs) . Therefore, it can be applied to tumors close to critical organs such as the esophagus, spinal cord, head, and brachial plexus .

Proton therapy systems use cyclotrons which are an order of magnitude more expensive than megavoltage linear accelerators (linacs). Hence, proton therapy is generally reserved for only the most critically conformal treatments such as :

• pediatric cancers
• re-treatment of previously irradiated tumors