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Introducing proton therapy – an advanced type of radiotherapy suitable for cancers located close to vital organs and for some childhood cancers and tumours. Discover the key indications and benefits for its use.
Radiation therapy, also known as radiotherapy, plays a crucial role in cancer treatment as a targeted approach to destroying cancer. It utilises high-energy radiation, either delivered externally (external beam radiation therapy) or internally (brachytherapy), to destroy cancer cell DNA and inhibit their growth and division.
The primary goals of radiotherapy are to:
Cure localised early-stage cancers
Reduce the risk of recurrence after surgery (adjuvant treatment)
Shrink tumours before surgery (neoadjuvant treatment)
Palliate symptoms in advanced cases
With careful treatment planning, radiotherapy maximises the destruction of cancer cells while sparing surrounding healthy tissues, with the aim to improve patients’ survival rates, alleviate symptoms and enhance their quality of life.
It is estimated that approximately 50% of cancer patients may receive radiotherapy as part of their treatment.
Proton therapy is a type of advanced radiation treatment that targets cancer cells using positively charged subatomic particles called protons. The unique physical properties of protons enable tumours to be targeted more precisely.
This potentially results in less damage to nearby healthy tissues and organs, and therefore less treatment-related side effects.
Figure 1 Proton therapy precisely targets the tumour and stops at a limited depth, resulting in lesser damage to nearby healthy tissues and organs, and fewer side effects.
Figure 2 The proton beam is delivered in very small ‘spots’ layer by layer, to treat complex-shaped tumours and reduce radiation to nearby normal tissues.
1. Precise targeting
Firstly, precise targeting can reduce radiation to nearby healthy organs, potentially reducing treatment-related side effects. This is particularly beneficial when treating tumours located near sensitive areas, such as the brain, spinal cord, eyes and other critical organs.
This also lends itself well to re-irradiation – when patients who have had a prior course of radiotherapy require a second course in recurrent cancers.
2. Dose escalation
Secondly, in certain situations, a higher dose may be delivered with protons compared to X-rays. This is known as dose escalation and has the potential for better tumour control.
Certain tumours, known as radioresistant tumours, are less responsive to conventional radiotherapy. Proton therapy has the potential to treat radioresistant tumours due to its unique properties.
It is important to note that before treating any patient with proton therapy, they must be reviewed by a multidisciplinary team comprising radiation oncologists, surgical oncologists, medical oncologists, etc., to ensure that all possible treatment options (including chemotherapy, surgery and radiotherapy) have been considered and evaluated and the most appropriate type of treatment is recommended based on their condition and post-treatment care plan.
Conventional radiotherapy is an effective and safe treatment modality that remains the gold standard for treating most solid cancers.
The side effects of radiation treatment depend on the area that is treated. For example, patients undergoing head and neck treatments may experience loss of taste, mucositis and radiation dermatitis, whereas patients undergoing radiation to the pelvis may experience diarrhoea and lower urinary tract symptoms.
Proton therapy can be recommended for a list of indications approved by the Ministry of Health (MOH). This includes most paediatric solid tumours, some adult brain cancers, head and neck cancers and prostate cancers as these patients will benefit the most from receiving proton therapy.
Click here to view the full list of MOH-approved indications for use of proton therapy in treatment.
Currently, the Goh Cheng Liang Proton Therapy Centre at the National Cancer Centre Singapore (NCCS) is the only facility offering proton therapy in the public sector in Singapore.
A major concern when treating childhood cancer with radiotherapy are the late side effects it can cause, which may occur months or even years after treatment.
Children are at an increased risk of these late toxicities compared to adults, due to the increased sensitivity of developing tissues and organs to radiotherapy. In addition, children have more at-risk years for the development of late side effects.
Proton therapy helps to mitigate the risk of late side effects as it allows for an overall lower exposure of the body to radiation.
The Goh Cheng Liang Proton Therapy Centre (GCLPTC) at NCCS, an advanced radiotherapy facility that offers proton therapy, started operations in June 2023.
Supported by a S$50 million gift from the Goh Foundation, the GCLPTC is the only such facility in the public sector in Singapore and one of few proton therapy centres in Southeast Asia.
The GCLPTC has installed a state-of-the-art synchrotron equipped with pencil beam scanning technology (PBS). PBS is a more precise and advanced technique of delivering proton beams.
This allows radiation oncologists to treat a tumour by adjusting the intensity of the beam to achieve the treatment dose using spot-scanning technology.
The planning and delivery of proton therapy is similar to conventional radiotherapy. As part of the planning process, patients undergo immobilisation with customised devices, and a CT simulation scan is done to measure the patient’s body and precisely mark the treatment areas.
If the proton plan is assessed to be a suitable treatment option for the patient, proton treatment will be recommended.
The GCLPTC, located at the basement 3 level of NCCS, has four treatment rooms, each equipped with a gantry system to deliver proton beams. At the backend, the treatment gantry has an internal diameter of five metres and weighs about 220 tonnes.
By rotating the nozzle around the patient, along with a high-precision robotic couch, the beam can be delivered from any angle to target tumours with pinpoint accuracy. A high degree of accuracy can be achieved as the beam can deliver a spot size as small as one millimetre in diameter.
The treatment rooms are also equipped with imaging systems to precisely position the patient for accurate beam delivery.
NCCS is committed to providing high quality, accessible cancer care to the population. The GCLPTC is available to all patients, and has a referral process and pathway for doctors to refer patients who need proton therapy treatment.
Patients receiving care at NCCS can speak to their doctors about whether proton therapy is suitable for them. They will be reviewed by a team of radiation oncologists to determine the most appropriate type of radiation treatment for their condition.
For GP referrals, please contact NCCS at 6436 8288 or email to firstname.lastname@example.org.
Dr Ng Wee Loon graduated from the National University of Singapore in 2005, and completed his basic and advanced specialist training in radiation oncology at the National Cancer Centre Singapore. He also did a fellowship in clinical oncology at the Clatterbridge Cancer Centre in the United Kingdom from 2013 to 2014, where he was involved in the treatment of ocular tumours using proton therapy.
He is a member of the Royal College of Radiologists (United Kingdom) and the Singapore Radiological Society. Dr Ng’s clinical areas of interest include thoracic, brain and ocular tumours. His current research focus is on organ motion in radiotherapy, and overcoming challenges in treatment planning of patients with prostheses. He is actively involved in the coaching of residents and junior doctors.
GP Appointment Hotline: 6436 8288
GPs can visit the website for more information on proton therapy or the GCLPTC.