Protons were first mooted as a medical treatment in 1946 by a US based physicist, Robert R. Wilson The first attempts to use proton radiation to treat patients began in the 1950s in nuclear physics research facilities. However, only a few areas of the body could be treated this way.
In the late 1970s, cancer treatment by proton therapy became possible with imaging advancements using sophisticated computer equipments for treatment delivery. Thereafter, established medical centers began offering proton therapy.
The prototype machines were built over large areas within University hospitals to promote research and develop protocols for appropriate treatments. Now compact, smaller machines have been developed by the industry and this has reduced the cost of treatment as well as cost of equipment and its housing.
Protons have similar biologic effect as the photons or X-Rays, the most commonly used form of radiation therapy till a few years ago. Protons are heavy charged particles and have a unique way of depositing their energy into tissues. Rather than causing damage through their entire path, they travel with minimal dose deposition along the path and deposit most of their energy at a distinct depth before stopping completely. This effect is known as the Bragg Peak and allows the largest dose to be delivered at the end of their track i.e. in the tumour. And beyond the Bragg peak, the dose falls to practically zero.
This quality of Protons protects the normal tissues that are lying in the path of the beam either before or after the position of cancers deep within the body.
Protons are best suited for treatments in young children and for cancers that lie close to neural pathways e.g. brain, eyes, spinal cord, lungs and heart. Another advantage of Protons in children is that the beam of energy does not cause any late effects like limb shortening or growth impairment.
Modern Proton therapy machines have intensity modulated proton therapy technology which utilize pencil beam scanning, allowing the radiation oncologist to prescribe treatment which ‘paints’ across the tumour volume, whilst sparing healthy tissues and organ.
The main advantages of proton therapy are that it is non-invasive with a high degree of accuracy and can be used to treat previously irradiated areas. Patients treated with proton therapy can maintain their current quality of life before and after treatment.
Proton radiation treatment has a very short life. After patients complete their treatment, they can leave the treatment room without any risks or radiation exposure to others. In all, treatment sessions typically last for 15-40 minutes with each beam only taking one to three minutes, and the complete course of treatment may be from one to 7-8 weeks, once per day, five times per week.