How Proton Therapy Works

What is Proton Therapy? 

Proton therapy is an advanced type of radiation treatment that targets cancer cells using positively charged subatomic particles called protons. The unique physical properties of protons enable tumours to be more precisely targeted compared to the x-rays used in conventional radiotherapy. This minimises damage to nearby healthy tissues and organs and therefore results in fewer treatment-related side effects. 

How is proton therapy different from conventional radiotherapy? 

Conventional radiotherapy delivers x-rays to the tumour. These electromagnetic waves carry no charge, allowing it to penetrate the body from one end to another. The x-ray beam gradually loses energy as it travels inside the patient’s body, resulting in some radiation to tissues beyond the tumour. This may cause damage to nearby healthy tissues and thus cause side effects. 

Proton therapy delivers a beam of positively-charged particles (called protons) that have a lower entrance dose and stop at a limited depth. This physical property of protons results in a significantly lower radiation dose, making it less damaging to nearby healthy tissues. 

Proton therapy has been shown to produce fewer side effects when compared to conventional radiotherapy. 

What are the main benefits of proton therapy? 

There are two main advantages of protons over conventional radiotherapy. Firstly, the reduced radiation exposure to nearby healthy tissues and organs reduces treatment-related side effects. Secondly, in certain cases, a higher dose can be delivered with protons compared to x-rays, giving the potential for better tumour control. 

How is proton therapy delivered? 

The planning and delivery of proton therapy is similar to conventional radiotherapy. As part of the pre-treatment planning process, patients undergo immobilization with customised devices and a CT simulation scan is done to measure and precisely mark the treatment areas. 

The most suitable conventional radiation plans and proton plans are generated for each patient for comparison. If the proton plan is assessed to be a better treatment option for the patient than the conventional radiation plan, proton treatment will be recommended. 

What are the possible side effects of proton therapy? 

The side effects a patient may experience depends on the area of the body that is being treated. Proton therapy has similar types of side effects to conventional x-ray based radiotherapy. However, the incidence and severity of radiation-associated side effects is expected to be lower due to the lower amount of radiation used in proton therapy.