The Evolution of Radiotherapy That Led Us to Arc Therapy
Radiotherapy has evolved a lot in the last 10 years. Traditionally treatment involved large square fields of radiation directed at a patient. The consequence of this was very high doses to healthy tissue around the tumour itself with considerable toxicity and side effects.
It was identified here that radiation needed to be shaped around the tumour in order to spare the healthy tissue from high doses. Multileaf Collimators (MLCs) were developed and the term Conformal radiotherapy was born. With the development of technology that allowed smaller and faster-moving precise MLCs, radiotherapy planning and delivery began to offer Intensity Modulated Radiotherapy (IMRT).
The premise of IMRT is to utilise these MLCs to divide the treatment beam into many small beamlets that will vary the intensity of the radiation dose and the shape of it across the whole tumour. This is particularly important for tumours located close to other healthy organs. Tumour dose is often limited by the tolerance of the surrounding tissue. By using MLCs to shape the radiation and shield those more sensitive organs it makes it possible to increase the dose to the tumour itself and improve treatment outcomes without compromising the surrounding healthy tissue.
What is Arc Therapy?
IMRT involves one static beam delivering the treatment at a set angle before moving onto the next desired angle, delivering more treatment there over and over as many times as needed to get an even dose around the whole tumour.
Arc therapy is different. Instead, it involves a continuous beam that automatically changes shape with the use of the MLCs and also continuously changes the intensity of the dose. One major advantage of this is treatment delivery time, as the beam is continuously on and not stopping and starting the time it takes to treat a patient can be greatly reduced. Evidence also shows the use of Arc therapy in proton treatments has improved LET distribution making it the obvious treatment choice.
To gantry or not to gantry?…that is the question
At the inception of Arc therapy, the option of delivering this treatment modality in anything but a supine position with a large rotating gantry was non-existent and has resulted in particle treatments such as Protons and Carbon being unable to move forward with this superior treatment delivery option. Most treatment facilities house fixed beam systems paired with a supine couch, limiting the number of beam angles possible and therefore indications treatable. The problem is that rotating gantries in this area of radiation therapy are very large and therefore very costly. A rotating proton gantry requires 100 tonnes of machinery moving around a patient. This also contributes to the engineering feat of continuously rotating such machinery to submillimetre accuracy.
The option of delivering gantry-less Arc therapy has been attempted before with the development of the PHASER (Pluri-directional High-Energy Agile Scanning Electron Radiotherapy) treatment machine at Stanford. It uses rapidly scanned beams from many angles using electromagnetic steering whilst the patient lies supine on a treatment couch negating the need for a rotating gantry.
(https://physicsworld.com/a/phaser-linac-will-translate-flash-radiotherapy-to-the-clinic/)
If you needed to change a lightbulb would you rotate the house or the light bulb?
The development of Leo Cancer Care’s unique patient positioning system that supports patients in an upright position whilst rotating them throws the doors wide open for existing fixed beam particle therapy facilities to begin to offer their patients Arc therapy.
Leo Cancer Care early on in their journey identified the benefit of rotating the smaller, lighter option, the patient, rather than the large, heavy, and very sophisticated technology which is the beam delivery system of the treatment machine. By doing this it is possible to utilise much smaller treatment rooms, allowing for Oncology facilities to optimise the space they have and keep costs down considerably.
There is extensive evidence that shows Arc therapy is a superior treatment option in photon, proton, and heavy ion therapies. Leo Cancer Care’s technology supports this treatment option in a practical way by allowing a continuous intensity modulated beam to be delivered whilst the patient slowly rotates around it. Research has also suggested that the upright position has clinical benefits which will improve intensity-modulated treatments such as reduced organ motion, tumour stability, and increased lung volumes all of which support the reduction of treatment margins, and potential dose escalation whilst increasing treatment accuracy.
Leo Cancer Care developed its technology to increase accessibility to life-saving treatments and also to improve the experience of radiation therapy for patients. The position is more comfortable, and supportive, it also allows users to maintain eye contact with their therapist as they are set up for treatment. That connection is vital in reducing anxiety and providing patient-centred care.
Please Note: The Leo Cancer Care technology is not commercially available and will not treat patients until the required regulatory approval has been achieved.
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