How does proton therapy work?

A treatment team maps the tumour and nearby organs with imaging. A [Proton Therapy System](/technology/proton-therapy-system/) accelerates protons and directs them into the body. As the particles slow, they release much of their radiation near the planned stopping point, called the Bragg peak. The aim is to treat the target while reducing radiation beyond it. This physical property can matter when a tumour lies close to sensitive structures, although suitability depends on tumour position, movement, previous treatment and the available plan. Proton therapy is one form of external radiation treatment and may be compared with [External Beam Radiotherapy](/treatments/radiation-oncology/external-beam-radiotherapy/).

Attend planning appointments so the team can create an individual immobilisation and beam plan. You may need to lie in the same position for each session. Follow instructions about skin care, medicines and food or drink. Keep the treatment area clean and report new skin changes, increasing tiredness, pain or difficulty swallowing, depending on the body region treated. Children may need extra support with positioning and staying still; families can discuss this when [Childhood Cancer](/conditions/childhood-cancer/) care is planned.

Contact the radiation team promptly for rapidly worsening pain, marked skin reaction, persistent vomiting, new weakness or trouble breathing. Seek emergency help for severe breathing difficulty, confusion or collapse. Side effects depend on the treated area and can appear during treatment or afterward, so use the contact number supplied by your centre.

Ask why proton therapy is suitable for your tumour, what nearby organs the plan protects, how many visits are expected, and what alternatives were considered. For a bone tumour such as [Chondrosarcoma](/conditions/chondrosarcoma/), ask how surgery and radiation are coordinated.