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Cancer Treatments | Proton Therapy

Radiation used for cancer treatment can be divided into 2 major types: Photon radiation (x-rays and gamma rays) and particle radiation (such as protons, neutrons, carbon ion beam, alpha particles and beta particles)

Protons are positively charged parts of atoms. A machine called a synchrotron or cyclotron speeds up the protons, which are then directed precisely at the tumour. After protons reach the desired place in the body, they deposit the specified radiation dose in the tumour.

With proton therapy, there is minimal radiation dose beyond the target area. Thus, it is able to deliver precise radiation dose to the tumour site while minimizing the damage to surrounding normal tissues and critical structures as compared to conventional radiation therapy.

How does Proton Therapy work?

Proton beams have a unique characteristic called the “Bragg peak”, which enables emission of the highest radiation dose at the set depth. Thus, we are able to control the proton beam to deposit a large focused amount of radiation right into a tumour. In proton therapy, the shape and depth of the ‘Bragg peak’ are precisely controlled to conform to the shape and size of a tumour, which enables radiation oncologists to provide a focused treatment on the targeted area, with little radiation dose beyond it.

Unlike proton therapy, conventional radiation therapy uses photons which enter the body and deposit most of its energy in normal tissues near the body surface, and then the energy reduces as it goes towards the center of the body. They also continue to penetrate through the tumor and irradiate the healthy tissue behind it. This undesirable pattern of energy placement can result in unnecessary damage to healthy tissue, thus increasing the side effects.

Differences between Radiation Therapy and Proton Therapy

Radiation Therapy and Proton Therapy are both used to treat cancer. They have similar aims of delivering high doses of radiation to the tumour while minimizing dose to the normal tissues.

So what makes them different?

Proton beam has a unique characteristic called the “Bragg peak”, which enables emission of the highest radiation dose at the set depth. Thus, we are able to control the proton beam to deposit a large focused amount of radiation right into a tumour. In proton therapy, the shape and depth of the ‘Bragg peak’ are precisely controlled to conform to the shape and size of a tumour, which enables radiation oncologists to provide a focused treatment on the targeted area.

Unlike proton therapy, conventional radiation therapy uses photons which enter the body and deposit most of its energy in normal tissues near the body surface, and then the energy reduces as it goes towards the center of the body. The photons also continue to pass through the tumor and release some radiation to the healthy tissue behind the tumour. This undesirable pattern of energy placement can result in unnecessary damage to healthy tissue, thus increasing the side effects experienced by the patient.

Benefits of Proton Therapy

  • High therapeutic ratio (maximum tumour control and minimum side effects)
  • Ability to irradiate tumours situated at close proximity to vulnerable organs e.g. small
    bowels and optic chiasm.
  • Reduces the possibility of secondary cancers caused by conventional radiation therapy,
    especially in children and young adults
  • An alternative for elderly and patients who are unfit for surgeries due to their medical
    comorbidities.
  • Treated on an outpatient basis.

Side effects of Proton Therapy

  • Proton therapy has far fewer side effects than conventional radiation therapy because it
    targets tumour site with high precision and minimizes normal tissue irradiation.
  • However it has been found that side effects appear differently on different patients.
    Symptoms of its side effects may differ depending on cancer site, direction of radiation,
    and radiation dose.
  • It is important to discuss with your oncologist before the treatment and fully understand
    the possible side effects/adverse reactions and how to manage them when they actually
    appear.

What’s in a State-of-the-art Proton Facility

In- room CT scanners or X-ray machines with cone- beam CT function allow precise and accurate matching of the target volume. In addition, our treatment table is controlled with a robotic system that transfers patient from in- room CT to treatment area.

With the use of these equipment, we are able to accomplish more precise proton therapy for our patients.

The latest proton therapy machines have ‘pencil-beam’ scanning which involves moving a small or ‘spot’ proton beam to ‘paint’ the tumour precisely in three dimensions. Simply put, it is like performing IMRT with the added natural advantage of the proton beam.

Planning Your Proton Therapy Journey

The patient selection criteria process involves a number of complex steps, and your oncologist will go through a series of evaluation to make sure that you are a suitable candidate.

In summary,

  • In- person consultation and patient evaluation for treatment suitability.
  • Customization of immobilization devices.
  • Treatment planning imaging like CT and MRI will be taken
  • Clinical treatment planning
  • Fabrication of beam shaping devices for precise treatment e.g. bolus and collimators
  • Treatment Rehearsal
  • Actual Treatment