What Is Proton Therapy?

Proton therapy is treatment delivered with particles. Protons are separated from hydrogen atoms and sped up in a particle accelerator and delivered to the patient. Protons stop at a predetermined distance in the patient instead of traveling through. They also deposit most of the dose at the tumour. On the other hand, X-rays from treatments like intensity modulated radiation therapy (IMRT) travel through and through the patient. X-rays also have a deposit a higher dose at the surface of the patient relative to the tumour itself. Thus, proton therapy has a better dosimetric profile.

What Are The Benefits Of Proton Therapy?

Proton therapy is useful in two scenarios:

  • Escalate dose
    • Keep the toxicity in adjacent organs constant but increase the radiation dose to the tumour
    • Example: curing more skull base chordomas without causing blindness
  • Reduce collateral radiation injury
    • Keep radiation to the tumour constant but reduce toxicity to adjacent normal organs
    • Example: curing the same rate of medulloblastomas but reducing the damage to heart and lungs

When Should We Consider Proton Therapy?

You should consider proton therapy for the following types of patients:

  • Young patients, especially children, as their risk of second cancer from therapy itself is higher
  • Radio-resistant tumours requiring dose escalation, e.g. chordoma, chondrosarcoma
  • Tumours in locations with many critical structures nearby, e.g. head and neck cancer, brain tumours, liver cancers, esophageal cancers etc
  • When the dose splash with conventional radiotherapy will be significant enough to cause more side effects, e.g. cranio-spinal irradiation