Bragg Peak brings with it a plethora of benefits What ’ s significant about protons is that they decelerate faster than photons – most radiation therapy machines , x-rays included , use photon beams . Protons also deposit more energy as they slow down , culminating in a peak , known as Bragg Peak . In other words , the Bragg Peak is a pinnacle that is visualised on a Bragg curve graph , a graph which plots the energy loss of ionizing radiation during its travel through matter .
Compared to electron or photon radiation , both of which have high entry doses – of 90-100 % relative energy – which then taper off , protons can enter the body at a 20 % dose before depositing all their energy at the delivery site , which when done right is the tumour . Because of this ability of protons to rapidly lose energy , proton beam therapy delivers an extremely high dose of radiation to a very localized site , which brings with it an abundance of benefits : minimal radiation to healthy tissue , reduced risk of secondary cancers , safe dose escalation associated with higher overall survival , reduced risk of radiation-induced malignancy in young people , and significantly lower risk of adverse side effects and toxicity .
In cases of brain tumours , being able to stop the depth of the radiation would lower IQ loss or , in children , lower growth disturbances . It also has particular applications to liver cancer as liver function is usually easily affected depending on the dose of conventional therapy . In general , proton therapy has the potential to deliver better outcomes and longer survival for patients .
What cancers does it treat ? Putting together the input of all specialists who presented at the event , proton therapy is beneficial in a wide range of cancers , including the brain , oesophageal , gastrointestinal , head and neck , liver , lymphoma , prostate , soft tissue , and spine . Proton therapy can be helpful to both adult and paediatric patients .
Disadvantages and concerns While this all sounds very promising , Dr Yang said that at the moment , not everyone can benefit from proton therapy : patients must be selected , so this is not a treatment option for anyone who wants it ; treatment is subject to review and approval from a multidisciplinary tumour board team .
On top of that , the cost of treatment is high due to the high costs of facility setup and maintenance .
According to Dr Ivan Tham , Radiation Oncologist at Mount Elizabeth Hospitals , Gleneagles Hospital and Parkway Cancer Centre , proton therapy can be less robust and more complex than photon ( x-ray ) treatment . “ Bragg Peak is sensitive , and so , any changes in the patient ’ s body can potentially affect treatment accuracy ”, he said . This makes all the difference between cure and toxicity . Hence , our system will have multiple layers of checks and quality assurance processes to ensure that our patients are
Children can benefit from proton therapy too
treated as effectively and as safely as possible . Dr Lee Kuo Ann , Radiation Oncologist at Mount Elizabeth Hospitals , Gleneagles Hospital and Parkway Cancer Centre agreed , stating that more care is required when performing proton therapy to ensure that the beam does not overshoot or undershoot the target . He added that as we only have retrospective data at the moment , randomised trials are needed to convince doctors , patients and payers that proton therapy is superior .
Proton therapy application to children One area that panellists Dr Lee Kim Shang , Radiation Oncologist and Dr Anselm Lee , Paediatric Medical Oncologist from Mount Elizabeth Hospitals , Gleneagles Hospital and Parkway Cancer Centre , devoted particular attention to is the difference between adult and paediatric oncology .
With high cure rates of paediatric cancers , children have many years of survival ahead of them after treatment , so any impact of long-term side-effects of treatment is greater . There are also particular concerns about reduced fertility , abnormal growth or development , second cancer , and endocrine dysfunction . In radiation therapy for children , special attention must be paid because the structures of the body are smaller , so there is a shorter separation between the target and any nearby healthy organ or tissue .
Dr Lee Kim Shang said that proton therapy is able to address many of these issues as proton beams can enter the body at a much lower entrance dose than conventional photon treatment and at the same time after discharging its tumour killing effect at the Bragg Peak , there is little or no dose in the normal tissue beyond the tumour leading to much less radiation exposure compared to photons . This leads to lower or less severe long term side effects mentioned earlier .
1 World Health Organisation Southeast Asia , https :// www . who . int /
southeastasia / news / detail / 04-02-2022-urgently-address-gaps-incancer-care-who 2 Ministry of Health Singapore , 2021
www . parkwaycancercentre . com
With high cure rates of paediatric cancers , children have many years of survival ahead of them after treatment , so any impact of long-term side-effects of treatment is greater .
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