Proton therapy or proton beam therapy is a type of external radiation therapy in which a beam of protons is used to produce radiation to the affected body part of the tumourous region. Proton therapy can be used for both cancerous and non-cancerous tumours depending upon the condition. This is different from that of the standard radiation therapy, which involves the use of X-rays. It can be used as a standalone treatment or in co-ordination with other treatments such as chemotherapy and surgery, depending upon the type of cancer and on the condition of the individual.
Proton therapy vs radiation treatment
Standard radiation treatment uses X-rays which comprise of both primary photons and secondary electrons. These X-rays place their energy on the path of the beam and can affect not just the targeted area but also the adjacent parts as well. These X-rays continue to cast their energy past the tumour and this is how it causes damage. It is the “exit dose” of the radiation therapy is the one that causes the damage to the adjacent healthy tissues.
However, in proton treatment, the medical professional can control the release of the protons concentrating most of its energy on the tumourous region. These are larger particles and they stick to the concentrated area alone. These positively charged particles interact with the electrons as they travel in the body to release energy. The place where the energy is released at the highest level is known as the “Bragg peak”. The proton beam can also comply to the shape and depth of the tumour. The major advantage of this treatment is that the medical professional can choose the location of the Bragg peak, stimulating the maximum damage of the tumorous cells while inducing a more negligible effect on the nearby healthy tissues.
Progress in proton treatment
In the initial phase, the proton therapy was mostly used in a scattering technique called the passive scattering beam delivery. However, now experts have formulated a new way named the pencil beam scanning delivery and the IMPT or the Intensity Modulated Proton Therapy.
Passive scattering beam delivery
This therapy is used to direct a wide beam towards the tumour. This was one of the first available commercial proton treatments. It delivers a homogenous dose across the target area.
Pencil beam scanning delivery
This is the more advanced form of proton treatment where the proton beam laterally sweeps over the target and delivers the required dose while conforming to the target tumour area. It is more effective in treating complex tumours such as brain, prostate and eye tumours.
Intensity Modulated Proton Therapy (IMPT)
IMPT is used to deliever highly potent and accurate doses of the protons to complicated or concave-shaped tumours that is very close to parts like the skull base, spinal cord, nasal and sinus cavities, and tongue among others.
What all can be treated using proton therapy?
This treatment is used in various cancer types such as :
- Pediatric treatments
- Eye tumours’
- Head and neck tumours
- Brain tumour
- Breast cancer
- Prostate cancer
- Gastrointestinal malignancy
- Hepatocellular carcinoma
- Recurring cancer conditions
What to expect in Proton Therapy
Preparing for proton treatment
Before undergoing the treatment, the healthcare team has to do some routine procedures to make you fit for the treatment. The first step is to determine a comfortable position for the patient during the radiation simulation. After this, they will mark the part of the body which has to be targeted with a marker. The treatment usually takes up to ten days after the simulation is done. They will also use an immobilization device on your body based on the target part so that you remain still throughout the procedure. If the target is the head, the patient will have a special mask fitted. They might use a cradle device if the target area is an arm or leg.
The next step is to determine how the target area has to be treated and how the protons can be disseminated in an effective way. The patient will be usually placed in the immoblization device as they conduct the imaging tests like the MRI ( Magnetic Resonance Imaging) and CT scans (Computerized Tomatography) to outline the target area. It might take from 45 minutes to one hour to complete this procedure.
How does it work?
The protons are emitted from an ion source where the hydrogen atoms are segregated into positive protons and negative electrons. The protons are then injected through a vacuum tube into a linear accelerator, and the proton beams enter the synchrotron or cyclotron, where their energy is accelerated and made appropriate for the body of the patient. The patient is made to lie in a device named the gantry, which is a circular device. It rotates around the person to direct the protons towards the tumourous cells.
During the treatment, the patient will be by themselves while the radiation expert will be in the adjacent room where they will observe and also communicate to the patient using an intercom. They will monitor the patient throughout the procedure. The time duration of the treatment can last from 15 minutes to 30 minutes depending upon the individual.
The medical professional will inform the patient about the possible side effects and the ways to control them. There are typically no side effects right after the treatment. The patient can resume their routine activities. However, the side effects can begin to show up after a few days. After up to four weeks after the treatment, you will be required to consult the doctor again. Some tests will be done to determine the changes in the tumour and to analyse whether the treatment has been effective.
Duration of Treatment
Proton beam therapy is usually an outpatient treatment. Typically, the standard course of treatment can range from two to eight weeks. The frequency of the treatment can be for five days a week but it can vary depending upon the type of tumour. The proton beam exposure lasts only for a few minutes, however, the patient might have to spend more time as the positioning of equipment and settings can often take time.
- Less amount of radiation is exposed to the healthy cells, decreasing the damage to the healthy cells
- Can aim for a higher radiation dose which might be beneficial for the patient without an increased risk.
- Has fewer side effects compared to standard radiation and will cause less nausea, hair loss and so on.
Possible Side effects
While proton therapy is told to cause fewer side effects compared to that of the standard radiation therapy, it too comes with its own side effects. The treatment can induce,
- Hair loss
- Cause redness in the skin of the affected area
- Digestive problems
This completely depends upon the reaction of the individual towards the treatment and can vary from person to person. It is essential to take the opinion of an expert before going ahead with this treatment.