Proton treatment is different from conventional x-ray radiation in that the energy distribution of protons  can be directed and deposited in tissue volumes designated by the physicians-in a three dimensional pattern from each beam used. It uses a beam of charged protons to target and destroy a more precise, defined area of cancerous cells. Unlike standard radiation, proton therapy delivers radiation energy only at the defined site of the tumor-not along the path through the body. This means that proton therapy spares significantly more surrounding healthy tissue and organs and produces fewer side effects for patients. Proton therapy also allows physicians to penetrate deeper tumors because higher levels of radiation can be used without fear of impact on surrounding healthy tissue.

Proton beam radiation is especially useful in the treatment of pediatric brain cancer, lung cancer, prostate cancer, and cancers of the spine. Because of the location of these tumors or proximity to vital organs, these cancers are more challenging to treat with standard radiation. 

Sources: oralcancerfoundation.org, proton-therapy.org,