Proton beam therapy (PBT)

Proton beam therapy (PBT)

Radiotherapy is a cancer treatment which uses radiation to kill cancer cells. Radiation also kills some healthy cells but they mainly recover. Radiotherapy techniques have improved significantly over the last decade with modern machines able to target the tumour better and reduce side effects – and increasingly with fewer numbers of visits for treatment. Some curative and palliative radiotherapy treatments are available now which were not available as recently as five years ago.

Conventional radiotherapy uses highly focused, high energy X-rays. Proton beam therapy (PBT) is an advanced form of radiotherapy, with radiation treatment delivered by proton beams rather than X-rays. A proton beam delivers some radiation to healthy tissue in reaching the tumour but very little radiation beyond the edge of the tumour being treated. Therefore, PBT is able to treat the cancer just as effectively but deliver less radiation to other parts of the body which surround the tumour.

For over 25 years PBT has been available at Clatterbridge Cancer Centre in the Wirral. The beam from this machine has a low energy so it cannot penetrate deep into the body. Therefore, it is only able to treat some cancers of the eye. High-energy proton machines suitable for treating deep-seated cancers have been available in the USA, Japan and some European countries for a number of years, but not yet in the UK.

PBT is being used increasingly to treat children with cancer. The chance of curing the cancer is no higher than with conventional radiotherapy but is likely to reduce the severity of the long-term side-effects, although it will not eliminate them altogether.

For adults with cancer the main use of PBT has been to treat cancers close to parts of the body which are sensitive to the damaging effects of radiation. For example, PBT is used to treat certain cancers at the base of the skull, deep inside the head and close to the brain, and cancers of the spine which are close to the spinal cord.

Currently the NHS provides access to PBT to patients who are likely to benefit by paying for them to have treatment abroad. Since 2008 increasing numbers of patients have been referred abroad for PBT, the majority of whom have been children. Most have been treated in Jacksonville, Florida and Oklahoma City in the USA, and some in Switzerland. The treatment, travel and accommodation costs are all funded by the NHS.

In 2008 an expert Proton Clinical Referral Panel was established. This panel advises on which patients with complex cancers are most likely to benefit from PBT in the short, medium and long-term. It also reviews all individual cases to ensure they meet criteria agreed by NHS England. Representatives from the panel have visited the PBT centres abroad to check that patients will receive the necessary high quality treatment. It is not enough to have the equipment for PBT. It is essential that the correct dose of radiation is delivered to the correct area. For children it is essential that they have access to the whole children’s cancer specialist team. It should also be stressed that PBT is rarely a treatment used on its own. The majority of patients will have had some surgery and/or chemotherapy in conjuction with the radiotherapy. It is important that PBT is given without any additional delay resulting from having to travel abroad.

PBT is delivered by machines which accelerate proton beams to high speeds. These machines are very large, complex and very expensive to build. It is planned to open two NHS PBT centres in the UK, one in The Christie Hospital, Manchester and one in University College Hospital, London. The first of these will start treating patients in 2018.

The two PBT centres in Manchester and London will be world-class. When they are fully operational in 2020, there will be only a relatively small proportion of patients requiring radiotherapy who will benefit from PBT. However this major investment will mean that those patients who might currently benefit from PBT will not have to travel abroad and will in future avoid major disruption to families’ lives. Possible new uses of PBT will be explored and developed. Close monitoring of outcomes and side effects is producing a significant evidence base for the future analysis of the benefits of PBT. The development of PBT in the UK will help NHS patients have access to a broad range of advanced radiotherapy technologies.

Further information about PBT services, including information for patients about referral abroad for treatment, is available from the NHS England website.

Please note that the information given here relates to England and not the devolved nations. The commissioning arrangements for the devolved nations have not yet been fully resolved.

Roberts Proton Therapy Center, Philadelphia
Roberts Proton Therapy Center, Philadelphia