an eye tumour receiving proton beam treatment

Cancer treatment: proton beam therapy coming to UK

You may remember the case of Ashya King, the boy who is currently ‘cancer-free’ after being taken overseas for proton therapy, so it seems to be good news that in 2018, the UK’s first National Health Service high-energy proton beam therapy facility will open. What are the challenges involved in bringing this game-changing treatment to Britain?

Hidden behind hoarding on Grafton Way, near Tottenham Court Road in London, a building is taking shape that will house a revolution in patient care in the UK – a high-energy proton beam therapy centre. The therapy, which hit the headlines in 2014 when the parents of the then-five-year-old Ashya King took him to Prague for treatment, looks set to improve the outcome for UK patients with certain difficult-to-treat cancers. Once operational in 2019, this new University College London Hospitals (UCLH) Foundation Trust facility – together with its sister centre at The Christie in Manchester, which is due to open in 2018 – will provide a national proton beam therapy service to cancer patients who are currently funded by the NHS for treatment overseas.

The government announced in 2012 that the joint bid from UCLH and The Christie NHS Foundation Trust to house the UK’s proton beam therapy facilities had been successful. In March 2015, £250m in government funding was approved, enabling preparatory work to start on both centres.

Construction at UCLH began in July 2015, following relocation of the central oxygen supply for the hospital and demolition of UCLH’s Rosenheim Building, which previously occupied part of the site. The proton beam therapy facility will be housed underground within a 10,600 square metre five-level building extending 33 metres below ground while a 24,000 square metre, six-storey hospital (comprising five storeys of treatment facilities and one plant level) for haematology and short-stay surgery patients will be built on top.

In total, the building will require just over 44,000 cubic metres of concrete reinforced with approximately 8,000 tonnes of steel. The excavation area is currently one of the largest in London and, by the time work is complete, around 80,000 cubic metres of soil will have been removed from the site. To ensure sufficient power is available to the facility, a new UK Power Networks prime substation will be located 2.5km away on Calshott Street and will be commissioned to support this and a number of other projects in the area.

One of the most challenging phases of the construction will occur in the first quarter of 2018 when the delicate but bulky proton beam therapy equipment will be installed, the largest individual element of which weighs 70 tonnes. Each part will have to be carefully and slowly lowered down to the basement level, including the three-storey high, 120-tonne treatment gantries needed to steer the proton beam into the treatment rooms. To create the required environment for installing the equipment, temporary mechanical and electrical plant rooms are being created that will eventually be housed within the above-ground hospital.

Once the equipment is running, some of the areas around the proton beam’s path will be radioactive so, to protect patients, visitors and staff, independent radiation safety experts have developed stringent shielding requirements for the building. These will be met via the construction of concrete walls up to 3m thick, together with 500 tonnes of 1.6m-thick steel plates in specific locations.

Innovative techniques

As there is no precedent for building this type of facility in the UK, the latest Building Information Modelling (BIM) methodology has been extensively used. This involves creating digital representations of all stages of the design and construction process in the form of 3D virtual models with detailed information embedded.

BIM also evolves the design in a collaborative way via analysis and discussion at regular meetings with all of the project team including the designers, contractors, equipment provider, clinicians and patients. As the construction contractor Bouygues UK explains, BIM allows the testing of ideas and for issues to be addressed ahead of actual construction work.

“The innovative BIM methodology undoubtedly minimised the risk of rework and clashes,” says UCLH’s construction and project lead, Tahir Ahmed. Optimisation of the design will be an ongoing process throughout the construction, as will working out logistics. For instance, the BIM software allowed Bouygues UK to model how best to pour the concrete each day in order to have the joints in areas that will not compromise the radiation shielding.

“One of the main challenges of the project is its location within a densely populated residential and commercial area surrounded by congested roads,” says Ahmed. This has been overcome by regular meetings with and cooperation from Transport for London, the local authority, the local community and the London Ambulance Service, as well as Bouygues UK and the proton beam therapy equipment provider Varian.

Perhaps surprisingly for a facility almost as deep as the London Underground network, one suspected problem they will not have to deal with is external vibration. Ahmed says the basement assessment impact studies revealed no vibration issues. Although the closest point of the site is just 10m from the Underground’s Northern Line, Bouygues UK says that the 20,000 cubic metres of concrete forming the therapy facility is dense enough to prevent vibration creating problems.

Complex kit

Since the building must wrap around the proton beam therapy system, before any designs could be finalised an equipment manufacturer had to be procured, explains Dr Simon Jolly, a lecturer in high energy physics at UCL and one of the technical advisers for the joint equipment procurement process with The Christie. “We had to make sure the equipment would fit on the compact site, and that it would meet the clinical requirements,” says Dr Jolly.

The clinical requirements are particularly complex, explains Derek D’Souza, head of radiotherapy physics at UCLH, because unlike many existing proton beam therapy centres, which are self-funding private facilities specialising in a particular type of cancer, this service will treat NHS patients. This relatively complex range of patients includes children, teenagers and adults with tumours in hard-to-treat places.

A single cyclotron particle accelerator will create the therapy beam that is fed via the gantries into each treatment room. “The cyclotron contains a superconducting magnet and sits in a liquid helium bath to make sure the magnet stays superconducting. You’ve got gantries three storeys tall and over 100 tonnes that have to rotate with millimetre accuracy so they can deliver the beam to the patient from any direction. That’s not run of the mill,” says Dr Jolly.

To maintain the required performance in such a complex system, D’Souza explains that in addition to a 14-hour clinical day, physics and engineering checks will be carried out for three hours every weekday, and for eight hours on Saturdays. “The facility will run 24-hours a day, and the rest of the time is handed over to the manufacturers [Varian], who will be maintaining and servicing the system for us under a contract,” he says.

Prior to the therapy centre opening, Varian will work with UCLH staff to test the system and ensure it meets the required specifications. There will also be “a clinical commissioning phase where the [UCLH] clinical physics team will perform characterisation tests for treatment planning and will be responsible for the calibration of the system,” explains D’Souza.

Refining proton therapy

Although the UCLH centre is a clinical rather than a research facility, D’Souza is expecting the two trusts will collect data on patient outcomes. The trusts are searching for a software system that could manage this amount of data and may have to commission a bespoke solution, he says. D’Souza also intends to maintain the UCLH radiotherapy department’s strong links with UCL, and hopes to accommodate proton physics research in areas such as detector technology and improving dose delivery.

Some research projects are already under way at UCL, including development of a prototype proton radiography system for treatment planning by Dr Paul Doolan from UCL’s Medical Physics and Biomedical Department. This uses a single detector to take a proton radiograph alongside the X-ray CT currently acquired when planning proton beam therapy delivery. While the X-ray accurately reveals the position of the tumour and surrounding healthy organs, a mathematical conversion of X-ray data is needed to predict the proton beam’s path because, unlike X-rays, protons stop within the body and also follow a curved path thanks to deflection by the tiny electric fields produced by our atoms. While this conversion is acceptable, Dr Doolan says combining data from a proton radiograph and an X-ray CT would reveal how protons interact with each patient.

“Currently protons have to go 3.5 per cent beyond the boundaries of a tumour to make sure the required dose is delivered. This system could enable targeting of treatment protons more closely to the tumour,” says Dr Doolan.

Dr Jamie McClelland from the Centre for Medical Image Computing at UCL is developing a computer model that reveals the motion of lung tumours as patients breathe. This could eventually guide the planning of proton beam therapy treatment for lung cancer.

Currently, lung tumour position is determined by combining several sets of CT images, each set of which has been acquired at a different point in the breathing cycle. However, as every breath we take tends to be slightly different, image artefacts and blurring can result in a larger volume than necessary being treated in order to ensure the entire tumour is reached.

The computer model combines the individual CT images with a signal charting the patient’s breathing (recorded from the movement of their skin) to produce a 3D animated model that reveals the breath-to-breath variations for that patient and so should enable more accurate dose delivery.

Dr McClelland is also working on a related model that would be built from cone-beam CT data, which is generated via a single rotation around the patient of a cone-shaped X-ray beam and routinely acquired immediately prior to treatment. “The long-term goal is to have the therapy beam follow the motion of the tumour,” he says.

Preparing for patients

For now, though, D’Souza is focusing on getting suitably qualified staff in place ready for accepting the first patients in three years’ time.

The contract with Varian allows UCLH physicists, radiographers and clinical staff to work-shadow at existing Varian proton beam therapy centres worldwide. These visits will be complemented with university-based study, D’Souza explains, adding that there is also a contractual option for his own engineering team to eventually take over the running of the UCLH service from Varian.

Dr Yen-Ching Chang, a consultant in clinical oncology and clinical lead for radiotherapy at UCLH, explains that the training programme for clinical staff has already started “with various consultants attending courses in protons, as well as a regular local teaching session led by a physicist with extensive first-hand experience gained in established proton beam therapy centres in the US.”

The end result of this intensively collaborative approach to design, building and service operation is on course to bring a range of benefits to UK patients. Dr Chang is optimistic that the ability to refer patients for treatment locally will help overcome both medical challenges – such as coordinating the timing of surgery and chemotherapy with radiotherapy – and social challenges such as travelling overseas for treatment.

“Having easy and timely access to protons will mean that the type of radiotherapy I can offer to a particular patient will be entirely defined by clinical need,” she states.

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