“Ask Dr. HKSH” – Proton Therapy

Dr. CHANG Tien Yee, Amy

Specialist in Clinical Oncology

Q1. What is the principle of proton therapy, an innovative cancer treatment technology?

Proton therapy, a form of particle beam therapy, is currently the most advanced radiotherapy modality used in tumour treatment. In conventional X-ray (photon)-based radiotherapy, when the radiation beam enters the tumour, it also penetrates the tumour and impacts the normal tissues behind it, causing side effects and complications.

The advantage of proton therapy lies in the physical properties of the Bragg peak. When the proton beam reaches the specified depth of the body to concentrate on the tumour, the tissues behind the tumour are unaffected by penetrating radiation, thereby significantly reducing the side effects and complications on normal tissues.

Q2. What are the advantages of proton therapy?

Proton therapy has three main advantages. First, it has fewer side effects due to its Bragg peak property, meaning there is no penetrative radiation beyond the tumour, greatly reducing side effects and future complications on normal tissue.

Secondly, for patients who need repeated radiation treatments, proton therapy is beneficial. If the patient has previously undergone traditional radiotherapy and there is recurrence near the previously treated area, proton therapy can deliver high radiation doses to these recurrent areas without causing additional damage to the previously irradiated normal tissue.

Lastly, proton therapy is suitable for paediatric cancer patients. Radiation therapy can lead to many types of complications affecting brain development, vision, hearing, and even secondary cancers. Proton therapy greatly reduces the side effects on normal tissues and significantly reduce complications and future side effects on related organs such as the brain.

Q3. For which types of cancer is proton therapy more effective?

Proton therapy is most effective for the cancers of the brain, head and neck, breast, prostate, and paediatric cancers. It is also particularly suitable for specific cases of liver, lung, oesophageal, gynaecological, and pancreatic cancers.

Q4. What is the process of proton therapy?

The process of proton therapy shares many similarities with traditional radiotherapy. First, doctors will develop a treatment plan to confirm the suitability of proton therapy. Then, a radiation design will be arranged where the patient undergoes a series of CT scans at a specific treatment position and with moulds. These images will be used to plan the target areas of the tumour and normal tissues. Once the plan is completed, doctors, physicists, and radiation therapists will confirm the plan meets all standards before proceeding to the next step of proton therapy.

Q5. What are the side effects of proton therapy?

Proton therapy, similar to traditional radiotherapy, may cause site-specific side effects based on the area treated. For example, breast cancer patients may experience skin reactions, and head and neck cancer patients may experience throat pain, reduced salivary gland function, and skin reactions.

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